CN-114825946-B - Isolated conversion device with magnetic bias balance control and magnetic bias balance control method

CN114825946BCN 114825946 BCN114825946 BCN 114825946BCN-114825946-B

Abstract

An isolated conversion device with magnetic bias balance control comprises an isolated converter, a controller and a magnetic bias balance circuit. The isolated converter comprises a transformer, and a primary side of the transformer comprises a primary side winding and at least one switch bridge arm. The controller is coupled to the at least one switch arm and provides a pulse width modulation signal set to control the at least one switch arm. The magnetic bias balancing circuit is coupled with two ends of the primary side winding and the controller, and provides compensation voltage to the controller according to the average value of the winding voltages of the two ends of the primary side winding. The controller adjusts the duty ratio of the pulse width modulation signal group according to the compensation voltage so as to correct the magnetic bias.

Inventors

LI ZHIXIAN
XIE YIPING
LIN HONGJIE
HUANG HONGYU
Pan Qiaoyin

Assignees

台达电子工业股份有限公司
台达电子工业股份有限公司

Dates

Publication Date: 20260421
Application Date: 20210128
Priority Date: 20210128

Claims (15)

1. An isolated switching device with magnetic bias balance control, comprising: An isolated converter including a transformer, a primary side of the transformer including a primary side winding and at least one switching leg; A controller coupled to the at least one switch arm and providing a PWM signal set for controlling the at least one switch arm, and A magnetic bias balance circuit coupled to the two ends of the primary winding and the controller for providing a compensation voltage to the controller according to a voltage average value of a winding voltage at the two ends of the primary winding, wherein the controller adjusts the duty ratio of the PWM signal group according to the compensation voltage, Wherein the bias balancing circuit comprises: a sampling circuit coupled to two ends of the primary winding and generating an average voltage related to the average value of the voltage, and An offset compensation circuit coupled to the sampling circuit and providing the compensation voltage according to the average voltage and a zero voltage.
2. The isolated switching device of claim 1, wherein the sampling circuit is a differential filter circuit, and the differential filter circuit comprises: an operational amplifier, including a first input terminal, a second input terminal and an output terminal, wherein the output terminal is coupled to the offset compensation circuit; a filter circuit coupled to two ends of the primary winding; a first voltage divider circuit including a first resistor and a second resistor connected in series, the first resistor being coupled to the filter circuit, and two ends of the second resistor being respectively coupled to the first input end and the output end, and The second voltage dividing circuit comprises a third resistor and a fourth resistor which are connected in series, the third resistor is coupled with the filter circuit, and two ends of the fourth resistor are respectively coupled with the second input end and a negative end.
3. The isolated switching device of claim 2, wherein the filter circuit comprises: one end of the first filter resistor is coupled with one end of the primary side winding, and the other end of the first filter resistor is coupled with the first resistor; A second filter resistor having one end coupled to the other end of the primary winding and the other end coupled to the third resistor, and One end of the filter capacitor is coupled with the other end of the first filter resistor, and the other end of the filter capacitor is coupled with the other end of the second filter resistor.
4. The isolated switching device of claim 1, wherein the offset compensation circuit is a proportional-integral controller, and the proportional-integral controller comprises: an operation circuit coupled to the sampling circuit for providing an error value according to the difference between the average voltage and the zero voltage; And the proportional-integral unit is used for receiving the error value and generating the compensation voltage according to the error value.
5. The isolated switching device of claim 1, wherein the at least one switching leg comprises: a first bridge arm including a first switch and a second switch connected in series, and The capacitor group is connected with the first bridge arm in parallel and comprises a first capacitor and a second capacitor which are connected in series; one end of the primary side winding is coupled with a node between the first switch and the second switch, and the other end of the primary side winding is coupled with a node between the first capacitor and the second capacitor, and the pulse width modulation signal group comprises a first control signal for controlling the first switch and a second control signal for controlling the second switch.
6. The isolated switching device of claim 5, wherein the compensation voltage provided by the bias balancing circuit is associated with a first bias direction of the transformer, the controller decreasing the duty cycle of the first control signal according to the compensation voltage associated with the first bias direction.
7. The isolated switching device of claim 5, wherein the compensation voltage provided by the bias balancing circuit is associated with a second bias direction of the transformer, the controller decreasing the duty cycle of the second control signal according to the compensation voltage associated with the second bias direction.
8. The isolated switching device of claim 1, wherein the at least one switching leg comprises: a first bridge arm including a first switch and a second switch connected in series, and The second bridge arm is connected with the first bridge arm in parallel and comprises a third switch and a fourth switch which are connected in series; One end of the primary side winding is coupled with a node between the first switch and the second switch, and the other end of the primary side winding is coupled with a node between the third switch and the fourth switch, and the pulse width modulation signal group comprises a first control signal for controlling the first switch, a second control signal for controlling the second switch, a third control signal for controlling the third switch and a fourth control signal for controlling the fourth switch.
9. The isolated switching device of claim 8, wherein the compensation voltage provided by the bias balancing circuit corresponds to a first bias direction of the transformer, and the controller decreases the duty cycle of the first control signal and the fourth control signal according to the compensation voltage corresponding to the first bias direction.
10. The isolated switching device of claim 8, wherein the compensation voltage provided by the bias balancing circuit corresponds to a second bias direction of the transformer, and the controller decreases the duty ratio of the second control signal and the third control signal according to the compensation voltage corresponding to the second bias direction.
11. The method for controlling the magnetic bias balance of the isolated conversion device comprises an isolated converter, wherein the isolated converter comprises a transformer and at least one switch bridge arm coupled with the primary side of the transformer, and the method for controlling the magnetic bias balance comprises the following steps: (a) Providing a pulse width modulation signal group to control the switching of the at least one switch bridge arm so that the isolated converter converts an input voltage into an output voltage; (b) Providing a compensation voltage corresponding to a magnetic bias of the transformer according to a winding voltage across a primary side winding of the transformer, and (C) Adjusting the duty ratio of the PWM signal group according to the compensation voltage to correct the magnetic bias, Wherein step (b) comprises: (b1) Generating an average voltage with respect to a voltage average value of the winding voltage; (b2) Providing an error value based on the difference between the average voltage and a zero voltage, and (B3) The compensation voltage is generated according to the error value.
12. The method of claim 11, wherein the pwm signal set comprises a first control signal and a second control signal for controlling the at least one switching leg, and step (c) comprises: (c11) Providing the compensation voltage associated with a first one of the bias directions, and (C12) The duty cycle of the first control signal is reduced according to the compensation voltage associated with the first magnetic bias direction.
13. The method of claim 11, wherein the pwm signal set comprises a first control signal and a second control signal for controlling the at least one switching leg, and step (c) comprises: (c21) Providing the compensation voltage corresponding to a second magnetic bias direction of the magnetic bias, and (C22) The duty cycle of the second control signal is reduced according to the compensation voltage corresponding to the second magnetic bias direction.
14. The method of claim 11, wherein the pwm signal set includes a first control signal, a second control signal, a third control signal, and a fourth control signal for controlling the at least one switching leg, and step (c) includes: (c31) Providing the compensation voltage corresponding to a first magnetic bias direction of the magnetic bias, and (C32) And reducing the duty ratio of the first control signal and the fourth control signal according to the compensation voltage corresponding to the first magnetic bias direction.
15. The method of claim 11, wherein the pwm signal set includes a first control signal, a second control signal, a third control signal, and a fourth control signal for controlling the at least one switching leg, and step (c) includes: (c41) Providing the compensation voltage corresponding to a second magnetic bias direction of the magnetic bias, and (C42) And reducing the duty ratio of the second control signal and the third control signal according to the compensation voltage corresponding to the second magnetic bias direction.

Description

Isolated conversion device with magnetic bias balance control and magnetic bias balance control method Technical Field The present invention relates to a method for controlling the magnetic bias balance of a conversion device, and more particularly to a method for controlling the magnetic bias balance of an isolated conversion device. Background Fig. 1A is a schematic diagram of a full-bridge phase-shift converter circuit. When the switching duty cycle is different due to the difference of hardware lines or the signals for controlling the switches Q1-Q4, the average of the positive and negative voltage spans of the transformer 12 is not zero, so that the magnetizing current generates a phenomenon (abbreviated as magnetic bias) with the average quantity being not zero, and finally, the excitation inductance of the transformer 12 is saturated, the inductance value is rapidly reduced, and the risk of overlarge current at the primary side of the converter is caused. Therefore, in the prior art, the capacitor C is typically connected in series to the primary side of the transformer 12 to balance the positive and negative half-cycle voltage across the transformer 12, so as to avoid the occurrence of the magnetic bias phenomenon. However, this control method requires adding a capacitor C to the circuit, which increases the circuit cost and the circuit size. Another common solution is shown in fig. 1B, where a full-bridge circuit incorporates a current sensor CT and uses a current peak control method, and the control method can make half the cycle of the bias switch close in advance due to higher current, so that the product of the voltage and time of one side of the bias switch can be reduced to achieve the effect of balancing the bias switch. However, this control method requires adding a set of current sensors CT to the circuit, which also increases the circuit cost and the circuit volume. Therefore, how to design an isolated switching device with bias balance control and a bias balance control method thereof without increasing the control mode of a current sensor and without increasing an isolated capacitor to balance the bias is a big subject to be studied by the inventor of the present disclosure. Disclosure of Invention In order to solve the above-mentioned problems, the present invention provides an isolated conversion device with magnetic bias balance control to overcome the problems of the prior art. The isolated conversion device comprises an isolated converter comprising a transformer, wherein the primary side of the transformer comprises a primary side winding and at least one switch bridge arm. The controller is coupled with at least one switch bridge arm and provides a pulse width modulation signal group to control the at least one switch bridge arm. And a magnetic bias balancing circuit coupled to the two ends of the primary winding and the controller and providing a compensation voltage to the controller according to the average value of the winding voltages at the two ends of the primary winding, wherein the controller adjusts the duty ratio of the pulse width modulation signal group according to the compensation voltage. In order to solve the above-mentioned problems, the present invention provides a magnetic bias balance control method of an isolated conversion device to overcome the problems of the prior art. Therefore, the isolated converter comprises a transformer and at least one switch bridge arm coupled with the primary side of the transformer, and the magnetic bias balance control method comprises the following steps of (a) providing a pulse width modulation signal group to control the switching of the at least one switch bridge arm so that the isolated converter converts an input voltage into an output voltage. (b) A compensation voltage corresponding to the magnetic bias of the transformer is provided according to the winding voltage across the primary side winding of the transformer. And (c) adjusting the duty cycle of the pulse width modulation signal set according to the compensation voltage to correct the magnetic bias. The invention has the main purpose and technical effect that the winding voltage at the two ends of the primary side winding of the sampling transformer is utilized, the average value is obtained through the filtering circuit, and the average value is controlled to be 0 through the controller to correct the magnetic bias, so that the control mode of the current sensor is not required to be increased, the isolation capacitance is not required to be increased, and the technical effects of reducing the circuit volume and the circuit cost are achieved. For a further understanding of the technology, means, and advantages of the present invention, reference should be made to the following detailed description of the invention and to the accompanying drawings, which are included to provide a further understanding of the invention, and are not intended to limit the invention