TWI439838B - Constant current mode controller of ac inverter - Google Patents

Description

Constant current mode controller in AC converter

The invention relates to an AC converter, in particular to a constant current mode controller disposed in an AC converter.

An AC inverter produces an AC output signal to drive a motor or other component. In general, the AC converter does not actively limit the initial current output at startup, so it may output excessive initial current at startup, affecting or even destroying components driven by the AC converter.

To solve the above and other problems, the present specification provides an embodiment of a constant current mode controller for an AC converter for controlling an output stage of an AC converter to generate an AC output signal. The controller includes a driver, a current sensor, a current feedback controller, and a selective controller. The driver is coupled to the output stage for driving the output stage to generate an AC output signal. The current sensor is coupled to the output stage for sensing the current level of the AC output signal to generate a current sensing signal. The current feedback controller is coupled to the current sensor for generating a current feedback control signal according to the current sensing signal. The selective controller is coupled to the current feedback controller and the driver for referring to the current feedback control signal, directly controlling the driver according to the voltage control signal, or controlling the driver according to the voltage control signal and the current feedback control signal.

The AC inverter of the embodiment can be provided with a soft start function of voltage and/or current, and can react quickly at the time of starting and/or operation, and can avoid overcurrent or overvoltage, so that it can be more stable. Drive the motor or other components at the rear end.

FIG. 1 is a schematic diagram of an embodiment of an AC inverter of the present invention. The AC inverter 100 may include a single-phase or multi-phase circuit, and FIG. 1 only illustrates one of the single-phase circuits of the AC inverter 100, or a multi-phase circuit. A phase circuit, or a circuit shared by multiple phases of the AC converter 100.

The AC inverter 100 of this embodiment includes a constant current mode controller 110 and a power stage 190. The controller 110 can control the output stage 190 to output an AC output signal to drive the motor or other components. In addition to including a power amplifier, the output stage 190 itself may include additional voltage and/or current feedback control mechanisms.

The controller 110 of this embodiment includes a driver 120, a current detector 130, a current feedback controller 140, and a selective controller 150. . The driver 120 can include a pulse-width modulation integrated circuit (PWMIC) controlled by the selective controller 150. The driver 120 can drive the output stage 190 to generate an AC output signal. The current sensor 130 senses the current level of the AC output signal to generate a current sense signal ID, and the current sensor 130 can be built into the output stage 190 in addition to being included in the controller 110. Based on the current sense signal ID, the current feedback controller 140 can generate a current feedback control signal IFBC. Referring to the current feedback control signal IFBC, the selective controller 150 can directly use a voltage control signal VC as the control signal CS to control the driver 120, or simultaneously generate a control signal according to the voltage control signal VC and the current feedback control signal IFBC. The CS controls the driver 120.

For example, when the current feedback control signal IFBC is greater than 1, when the average current level of the AC output signal is less than a preset current threshold, it means that no overcurrent occurs, and at this time, the selectivity The controller 150 can directly use the voltage control signal VC as the control signal CS to control the driver 120, and the control signal CS does not cause the driver 120 to drive the output stage 190 to lower the average current level of the AC output signal. At this time, the phase of the AC converter 100 shown in FIG. 1 is in a constant voltage (CV) mode unless the phase of the AC converter 100 other than that shown in FIG. 1 has been switched to a constant current. In the (constant current, CC) mode, the phase shown in the AC converter 100 can continue to stay in the constant voltage mode.

When the current feedback control signal IFBC is less than 1, when the average current level of the AC output signal is greater than the preset current threshold, it represents that an overcurrent may have occurred. At this time, the selective controller 150 can apply the voltage. The control signal VC and the current feedback control signal IFBC less than 1 are multiplied to generate a control signal CS to control the driver 120. In other words, the control signal CS at this time will be the voltage control signal VC and the current feedback control signal IFBC. Product signal. The control signal CS will cause the driver 120 to drive the output stage 190 to lower the current level of the AC output signal. At this time, the AC converter 100 is shown in the constant current mode, and the AC converter 100 can switch the other phases not shown in FIG. 1 to the constant current mode.

2 is a schematic diagram of an embodiment of the current feedback controller 140 of FIG. The current feedback controller 140 of the present embodiment includes an analog-to-digital converter (ADC) 141, a digital signal processor (DSP) 143, a digital analog converter (DAC) 145, and a current compensator. 147. The analog-to-digital converter 141 can sample the current sensing signal ID multiple times in each cycle of the AC output signal to generate a plurality of digital sampling values, and the analog digital converter 141 sequentially generates digital sampling values to form a digital current sensing. Signal DID. According to the digital current sensing signal DID, the digital signal processor 143 can generate a digital level value DL representing the average current level of the AC output signal. For example, the digital level value DL can represent the current level of the AC output signal. Root-mean-square (RMS) value. The digital analog converter 145 can convert the digital level value DL into a DC level DCL. The higher the DC level DCL, the larger the rms current of the AC output signal. By comparing the DC level DCL and a reference level RL, the current compensator 147 can determine whether the average current level of the AC output signal is greater than a preset current threshold, and output the aforementioned current feedback control signal IFBC for selection. Sex controller 150. For example, when the DC level DCL is greater than the reference level RL, the current compensator 147 can make the current feedback control signal IFBC less than 1; when the DC level DCL is less than the reference level RL, the current compensator 147 can make the current The feedback control signal IFBC is greater than one.

In order to allow the AC inverter 100 to have a faster response speed (even when the AC inverter 100 is just started), the digital signal processor 143 can use a moving window of length M times the AC output signal period. To calculate the digital level value DL, and update the digital level value DL a total of N times in each cycle of the AC output signal, and when the received digital sample value has not yet reached the number of samples that can be covered by the mobile computing window, That is, the digital level value DL is pre-generated based on the digital sample value that has received the insufficient number. Among them, M and N are both greater than 1.

For example, suppose M=2 and N=3, and the analog-to-digital converter 141 sequentially samples the D1~D6 samples in the first cycle of the AC output signal, in the second cycle. Sequential sampling produces a total of 6 digital sample values of D7~D12, and samples are sequentially sampled in the third cycle to generate 6 digital samples of D13~D18, and so on. Although the digital signal processor 143 does not obtain the number of samples that the mobile computing window can contain before receiving the digital sample value D12 (that is, a total of 12 samples for 2 cycles), the digital signal processor 143 can receive the digital sample. After the value D2, the digital level value DL is generated in advance according to the digital sample value D1~D2, and after receiving the digital sample value D4, the digital level value DL, ... is generated according to the digital sampled value D1~D4, and the digital number is received. After the sample value D10, the digit level value DL is generated in advance according to the digital sample values D1 to D10. After that, the digital signal processor 143 can generate a digital bit value DL according to the digital sample value D12 after receiving the digital sample value D12 (in this case, it is not "pre-"generated), and according to the digital value after receiving the digital sample value D14. The sampled value D3~D14 generates the digital level value DL. After receiving the digital sample value D16, the digital level value DL is generated according to the digital sample value D5~D16, and the digital sample value D18 is generated according to the digital sample value D7~D18. The digit value DL, and so on.

In addition, the controller 110 may further include a current soft start unit 310 and/or a voltage soft start unit 320 as shown in FIG. The current soft start unit 310 is used to gradually increase the reference level RL from a lower initial value to a target value when the AC converter 100 is started (instead of directly locking the reference level RL to the target value), The AC inverter 100 is prevented from being overcurrent when it is just started. Similarly, the voltage soft start unit 320 is used to gradually increase the voltage control signal VC from a lower initial value to a target value when the AC converter 100 is started (rather than directly locking the voltage control signal VC to a target value). ) to avoid the situation where the AC inverter 100 is facing an overvoltage just after starting up.

As described above, if the AC inverter 100 includes a multi-phase circuit, the AC converter 100 can switch all other phase circuits to the constant current mode as long as the circuit of any phase enters the constant current mode. . Assuming that the AC converter 100 includes a K phase as shown in FIG. 1 and K is a positive integer greater than one, the AC converter 100 may further include a mode selection logic shared by multiple phases. When the circuit for any phase of the AC inverter 100 enters the constant current mode, the circuits of the other phases of the AC converter 100 are switched to the constant current mode. Figure 4 is an example of this mode selection logic, in this example, the mode selection logic is implemented by OR Gate 410. The signal CC_k received by the gate 410 can be generated by the current compensator 147 in the kth phase circuit of the AC converter 100, and the variable k is a positive integer less than or equal to K. If the signal CC_k is equal to 0, it represents an AC converter. The kth phase circuit of 100 is still in the constant voltage mode. If the signal CC_k is equal to 1, it indicates that the kth phase circuit of the AC converter 100 has entered the constant current mode. If all the CC signals of CC_1~CC_K are equal to 0, or the gate 410 can output 0 to the selective controller 150 in each phase circuit of the AC inverter 100, the phase circuits of the AC converter 100 are allowed to stay at the constant voltage. mode. If any one or more of the CC signals CC_1~CC_K are equal to 1, or the gate 410 can output 1 to the selective controller 150 in each phase circuit of the AC inverter 100 to control each of the AC inverters 100. The phase circuits all enter the constant current mode.

The AC inverter 100 described in the above embodiments can be provided with a voltage and/or current soft start function, and can quickly react at the time of startup and/or operation, and can avoid overcurrent or overvoltage conditions, so The motor or other components of the rear end can be driven more stably.

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

100. . . AC converter

110. . . Controller

120. . . driver

130. . . Current sensor

140. . . Current feedback controller

141. . . Analog digital converter

143. . . Digital signal processor

145. . . Digital analog converter

147. . . Current compensator

150. . . Selective controller

190. . . Output stage

310. . . Current soft start unit

320. . . Voltage soft start unit

410. . . Gate

FIG. 1 is a schematic diagram of an embodiment of an AC inverter according to the present invention.

2 is a schematic diagram of an embodiment of the current feedback controller of FIG. 1.

3 is a schematic diagram of an embodiment of a current soft start unit and a voltage soft start unit that may be further included in the current feedback controller of FIG. 1.

4 is a schematic diagram of an embodiment of mode selection logic that may be further included in the current feedback controller of FIG. 1.

100. . . AC converter

110. . . Controller

120. . . driver

130. . . Current sensor

140. . . Current feedback controller

150. . . Selective controller

190. . . Output stage

Claims (10)

A constant current mode controller is disposed in an AC converter for controlling an output stage of the AC converter to generate an AC output signal, the controller comprising: a driver coupled to the output stage, The current output sensor is configured to generate the current output signal, and a current sensor is coupled to the output stage for sensing a current level of the AC output signal to generate a current sensing signal; a current feedback control The current sensor is coupled to the current sensor for generating a current feedback control signal according to the current sensing signal; and a selective controller coupled to the current feedback controller and the driver for reference The current feedback control signal controls the driver according to a voltage control signal, or simultaneously controls the driver according to the voltage control signal and the current feedback control signal. The controller of claim 1, wherein when the current feedback control signal indicates that the average current level of the AC output signal is lower than a predetermined current level, the selective controller directly controls the voltage according to the voltage. a signal to control the driver, and when the current feedback control signal indicates that the average current level of the AC output signal is higher than the preset current level, the selective controller returns the control signal according to the voltage control signal and the current A product signal to control the drive. The controller of claim 1, wherein the current feedback controller comprises: an analog-to-digital converter coupled to the current sensor for converting the current sensing signal into a digital position a digital signal processor coupled to the analog-to-digital converter for generating a digit value representative of an average current level of the AC output signal according to the digital current sensing signal; a digital analogy a converter coupled to the digital signal processor for converting the digital level value to a DC level; and a current compensator coupled to the digital analog converter and the selective controller The DC level is compared to a reference level to generate the current feedback control signal. The controller of claim 3, wherein the digital level value represents a root mean square value of a current level of the AC output signal. The controller of claim 3, wherein the digital signal processor calculates the digit value by using a mobile computing window having a length M times the AC output signal period, and M is greater than 1. The controller of claim 5, wherein the digital signal processor starts to generate the digital level value before the AC output signal reaches M cycles. The controller of claim 3, wherein the digital signal processor updates the digit value N times in each cycle of the AC output signal, and N is greater than 1. The controller of claim 3, further comprising a current soft start unit coupled to the current compensator for providing the reference level and gradually increasing the voltage when the AC converter is activated. Reference level. The controller of claim 1, further comprising a voltage soft start unit coupled to the selective controller for providing the voltage control signal and gradually increasing when the AC converter is activated. The voltage control signal. The controller of claim 1, further comprising a mode selection logic for controlling another current controller of the controller to enter the current control mode when the selective controller enters a current control mode Control mode.