TWI525970B - Power supply with current correction function - Google Patents

Description

Power supply with current correction function

The invention relates to a power supply, in particular to a power supply with current correction function.

Referring to FIG. 5 , the prior art power supply 20 has an input current measurement mode in which a current transformer 21 is disposed at an input end of the power supply 20 , and the current comparator 21 is coupled. The input current (I _CT ) is detected. However, when the comparator 21 is used to measure the input current of the power supply 20, the switching state of a bridge converter 22 at the input of the power supply 20 affects the measurement result of the comparator 21. For example, when the load state of the output of the power supply 20 is light load, the switching state of the bridge converter 22 is hard switching, and at the time of hard switching, the feedback value of the current comparator 21 is affected. The influence, the generation of the glitch, leads to errors in the current measurement results.

On the other hand, the output current measurement method of the power supply 20 of the prior art uses a measuring resistor R in series with the output end of the power supply 20, and detects the voltage across the measuring resistor R to convert the voltage across the voltage. Into the output current I _R . However, since the detecting resistor R is connected in series to the output end of the power supply 20, an output current continuously flows through the detecting resistor R to cause additional power loss, resulting in waste of electric energy. Therefore, the current measurement technique of the prior art power supply 20 is necessary to be further improved.

In view of the shortcomings of current power supply current measurement methods that are affected by the switching state of the bridge converter, resulting in measurement error, and the inductive resistance of the series measurement resistor, the main purpose of the present invention is to provide a current. Corrected power supply to improve measurement accuracy and reduce additional power loss.

To achieve the above objective, the power supply with current correction function of the present invention comprises: a bridge converter having a DC input terminal and an AC output terminal; a transformer having a primary side and a secondary side, The primary side is connected to the AC output end of the bridge converter; a rectifier having an AC input end and a DC output end, the AC input end being connected to the secondary side of the transformer; a current comparator connected a DC input terminal of the bridge converter to detect an input current of the bridge converter and output an input current signal; a first adjustment unit connected to the current comparator to receive the input current signal And multiplying the input current signal by a first magnification and adding a first compensation value to output a first current signal; or an ORing FET connected to the DC output of the rectifier a current measuring unit connected in parallel with the OR field effect transistor to detect an output current of the rectifier according to a voltage across the OR field and output an output current a second adjusting unit is connected to the current measuring unit to receive the output current signal, and multiply the output current signal by a second multiple and a second compensation value to output a second current a micro processing unit connected to the first adjusting unit and the second adjusting unit to receive the first current signal and the second current signal, and accordingly generate a current measuring signal; wherein the micro processing The device is preset to have a first current interval and a second current interval, wherein the current value corresponding to the first current interval is smaller than a current value corresponding to the second current region, and the first current signal or the second current When the current value corresponding to the signal falls in the first current interval, the current measurement signal is equal to the second current signal, and when the current value corresponding to the first current signal or the second current signal falls within the first In the two current interval, the current measurement signal is equal to the first current signal.

The present invention simultaneously detects the input current signal by the current comparator, and the current measuring unit detects the output current signal, and respectively generates the first current signal and the second current signal after the magnification adjustment and compensation, and according to The current measurement signal is generated. When the first current signal or the second current signal falls in the first current interval, the second current signal is used as the current measurement signal, and the first current signal or the second current signal is used. When the second current interval falls, the first current signal is used as the current measurement signal.

When the current value corresponding to the first current signal or the second current signal falls within the first current interval, the switching state of the bridge converter is hard-switched, and represents a power supply using the current measuring circuit of the present invention. The load of the device is in a light load state, and the first current signal is generated according to the current detector, but when the bridge converter is hard-switched, the feedback value of the current transformer is affected, causing a surge Generated, resulting in errors in the measurement results. Therefore, when the bridge converter is hard-switched, the current measuring unit detects the second current signal generated by the voltage across the field effect transistor as the current measuring signal to avoid the current flow. The error produced by the device affects the measurement result.

However, when the current value corresponding to the first current signal or the second current signal falls in the second current interval, the switching state of the bridge converter is softly switched, and represents a power supply using the current measuring circuit of the present invention. The load of the device is in a heavy load state, which leads to an increase in the temperature of the output terminal, which affects the measurement result of the current measuring unit of the current measuring unit, so when the bridge converter is switched softly, the system is adopted. The first current signal generated by the current detector is used as the current measurement signal to prevent the temperature from affecting the measurement result.

And the present invention obtains the second current signal by measuring the voltage across the field effect transistor at the output end, and the OR circuit of the field effect transistor system power supply is used as a necessary component in parallel application, so the present invention There is no additional measuring resistor to measure the current value at the output end. The original components in the power supply are used to achieve the purpose of current detection to further reduce power loss.

By determining the magnitude of the current value corresponding to the first current signal or the second current signal, the present invention uses different current detection signals when falling in the first current interval or the second current interval, which not only avoids The measurement result error caused by the switching mode, and the measurement error caused by the temperature is avoided, so as to further eliminate the measurement error, improve the current measurement accuracy, and reduce the additional power loss.

The technical means adopted by the present invention for achieving the intended purpose of creation are further explained below in conjunction with the drawings and preferred embodiments of the present invention.

Referring to FIG. 1 , the present invention is a power supply 10 with current correction function. The power supply 10 with current correction function includes a bridge converter 11 , a transformer 12 , a rectifier 13 , and a ratio A current transformer (14), a first adjusting unit 15, an ORing FET 16, an output current measuring unit 17, a second adjusting unit 18, and a micro processing unit 19. The OR field effect transistor 16 is the same as a general field effect transistor, but is specifically referred to as or in the field effect transistor 16 because of its application and mode of operation. The bridge converter 11 is a phase shifting full-bridge converter or a half-bridge converter. In the preferred embodiment, a phase-shifted full-bridge converter is taken as an example.

The bridge converter 11 has a DC input terminal 111 and an AC output terminal 112. The transformer 12 has a primary side 121 and a secondary side 122 that is coupled to the AC output 112 of the bridge converter 11. The rectifier 13 has an AC input terminal 131 and a DC output terminal 132. The AC input terminal 131 is connected to the secondary side 122 of the transformer 12.

The current comparator 14 is connected to the DC input terminal 111 of the bridge converter 11 to detect the input current of the bridge converter 11 and output an input current signal. The first adjusting unit 15 is connected to the current comparator 14 to receive the input current signal, multiply the input current signal by a first multiple rate and a first compensation value, and output a first current signal. S1.

The OR field effect transistor 16 is coupled to the DC output 132 of the rectifier 13. The current measuring unit 17 is connected in parallel with the OR field effect transistor 16 to detect the output current of the rectifier 13 according to the voltage across the OR field transistor 16, and output an output current signal. The second adjusting unit 18 is connected to the current measuring unit 17 to receive the output current signal, multiply the output current signal by a second multiple and add a second compensation value, and output a second current. Signal S2.

The micro processing unit 19 is connected to the output ends of the first adjusting unit 15 and the second adjusting unit 18, and receives the first current signal S1 and the second current signal S2, thereby outputting a current measuring signal S3. . As shown in FIG. 2A and FIG. 2B, the micro processing unit 19 presets a first current interval and a second current interval, and the current value corresponding to the first current interval is smaller than the second current interval. Corresponding current value. When the current value corresponding to the first current signal S1 or the second current signal S2 falls in the first current interval, that is, when the switching state of the bridge converter 11 is hard switching and the load is light load, the The current measurement signal S3 is equal to the second current signal S2, that is, the I _Oring curve in FIG. 2A, and the current value corresponding to the first current signal S1 or the second current signal S2 falls within the second current interval. When the switching state of the bridge converter 11 is softly switched and the load is heavy, the current measuring signal S3 is equal to the first current signal S1, that is, the I _CT curve in FIG. 2A. In summary, the current measurement signal S3 is also the I _detect curve in FIG. 2B. In the preferred embodiment, the microprocessor unit 19 is further preset with a threshold value, and the current value corresponding to the first current interval is less than the threshold value, and the current value corresponding to the second current interval is greater than Or equal to the threshold.

The invention simultaneously detects the input current of the bridge converter 11 and the output current of the rectifier 13, and determines the current measurement signal according to the switching state of the bridge converter 11 to ensure the accuracy of the measured current signal. Degree, to avoid changes in other parameters affect the measurement results.

When the current value corresponding to the first current signal S1 or the second current signal S2 falls within the first current interval, the bridge converter 11 is operated in a hard switching phase, that is, when the power supply is loaded. When the load is light, since the actual output current I _OUT is proportional to the load level of the power supply, the first current signal S1 or the second current signal S2 is positively correlated with the actual output current I _OUT . When the first current signal S1 or the second current signal S2 is less than the threshold, that is, when the first current interval falls, the current divider 14 may cause a specific flow because the bridge converter 11 is in a hard switching state. The error of the detection result of the device 14. In the first current interval, after the measurement result of the current comparator 14 is adjusted by the first adjusting unit 15, as shown by the dotted line in FIG. 2, that is, the I _CT curve, the glitch caused by the hard switching causes the detection. The obtained input current changes, so the detection result of the current transformer 14 cannot be used in the hard switching state. However, the output current detected by the current measuring unit 17 is not affected by the switching state of the bridge converter 11, and the actual output current I _OUT can be accurately detected. Therefore, when the bridge converter 11 is hard-switched, the second current signal S2 generated by the second adjusting unit 18, that is, the I _Oring curve, is used as the current measuring signal S3 as a current measurement result. The error caused by the influence of the switching state of the bridge converter 11 is avoided.

When the current value corresponding to the first current signal S1 or the second current signal S2 falls within the second current interval, the bridge converter 11 is operated in a soft switching phase, and at this time, the current comparator 14 The measurement result is close to the actual input current and can accurately reflect the input current. However, the output current detected by the current measuring unit 17 is generated according to the voltage across the OR circuit and the on-resistance of the field-effect transistor 16, and the on-resistance of the field-effect transistor 16 is affected by the temperature according to the OR. Therefore, when the second current signal S2 is greater than the threshold, that is, when the second current interval falls, the actual output current I _OUT increases as the second current signal increases by S2, and the load is also aggravated. Increasing the temperature of the load terminal, thereby causing the temperature of the OR field effect transistor 16 to rise accordingly, so that the error between the measurement result of the OR field effect transistor 16 and the actual output current I _OUT is also increased. . Therefore, when the current value corresponding to the first current signal S1 or the second current signal S2 falls in the second current interval, the first current signal generated by the current comparator 14 through the first adjusting unit 15 is used. S1, that is, the I _CT curve, is used as the current measurement signal S3 as the current measurement result to avoid the error caused by the orbital effect transistor 16 being affected by the temperature. In summary, the current measurement signal S3 is equivalent to the second current signal S2 in the hard switching state, that is, the I _Oring curve, and is equal to the first current signal S1, that is, the I _CT curve in the soft switching state, so the current The measurement signal S3 is an I _detect curve. In addition, the present invention detects the input and output currents by the current comparator 14 and the OR field effect transistor 16, and does not provide a sense resistor, thereby saving power loss.

The function of the first adjusting unit 15 is to adaptively adjust the input current signal detected by the current comparator 14, and the second adjusting unit 18 functions as the output current detected by the current measuring unit 17. The signal is adjusted for fitness. For example, when the user needs to know the output current value of the power supply, the first adjusting unit 15 transmits the input detected by the current divider 14 through the first magnification and the first compensation value. The input current value corresponding to the current signal is matched to the output current value to generate the first current signal, and the second current signal is the output current value corresponding to the output current signal measured by the current measuring unit 17, thereby unifying The reference is such that the current measuring signal S3 generated by the micro processing unit 19 is equivalent to the output current signal for the user to use. That is to say, when the user needs to know the output current value of the power supply, since the input current and the output current of the power supply are adjusted by the transformer 12, the turns ratio of the transformer is N1. :N2, so the relationship between the input current I _{IN of} the power supply and the output current I _OUT is: .

Wherein the I _offset is an error compensation caused by the loss of the transmission process, so the current comparator 14 multiplies the detected input current by the first magnification (N1/N2), and adds the first compensation value (I _Offset ), the input current detected by the current comparator 14 can be matched to the output current for use by the microprocessor unit 19.

On the other hand, when the user needs to detect the input current value of the power supply, the second adjustment unit 18 can measure the current measurement unit 17 through the second magnification and the second compensation value. The output current value corresponding to the output current signal is matched to the input current value to make the current measurement signal S3 generated by the micro processing unit 19 equal to the input current signal for the user to use.

The current measurement signal S3 generated by the micro processing unit 19 is transmitted to a control unit 191 electrically connected to the micro processing unit 19, and the control unit 191 is based on the current measurement signal S3 to the bridge converter 11. The adjustment of the switching control is performed to optimize the conversion efficiency of the power supply 10.

Referring to FIG. 2C, the micro processing unit 19 further presets a first comparison value, a second comparison value, and a third current interval. The third current interval is between the first current interval and the first Between the two current intervals. The current value corresponding to the first current interval is smaller than the first comparison value, and the current value corresponding to the second current interval is greater than the second comparison value, and the current value corresponding to the third current interval is The first comparison value is between the second comparison value. When the first current signal S1 or the second current signal S2 is smaller than the first comparison value, it falls in the first current interval, and the second current signal S2 is used as the current measurement signal S3. When the first current signal S1 or the second current signal S2 is greater than the second comparison value, it falls within the second current interval, and the first current signal S1 is used as the current measurement signal S3. When the first current signal S1 or the second current signal S2 is between the first comparison value and the second comparison value, that is, falling in the third current interval, continuously comparing the first current signal S1 and The magnitude of the second current signal S2 is taken as the current measurement signal S3. In summary, the current measurement signal S3 is also the I _detect curve in FIG. 2B. In the preferred embodiment, the micro processing unit 19 performs only when the current value corresponding to the first current signal S1 or the second current signal is between the first comparison value and the second comparison value. The operation of the size is compared to reduce the amount of computation of the microprocessor unit 19.

For example, when the current value corresponding to the second current signal S2 is equal to the second comparison value, as shown in FIG. 2C, the current value corresponding to the first current signal S1 and the second current signal S2 is compared. The current value corresponding to the second current signal S2 is as shown in P2 of FIG. 2C, and the current value corresponding to the first current signal S1 is as shown in P1 of FIG. 2C. At this time, the first current signal S1 corresponds to The current value is smaller than the current value corresponding to the second current signal S2. Therefore, the current value corresponding to the first current signal is used as the current value of the current measurement signal S3.

Referring to FIG. 3 together, the third preferred embodiment for determining the switching state of the bridge converter 11 is performed by the micro processing unit 19 to: determine the first current signal or the second current signal. a size (S11); when the first current signal or the second current signal is less than a first comparison value, the second current signal is used as the current measurement signal (S12); when the first current signal or When the second current signal is greater than a second comparison value, the first current signal is used as the current measurement signal (S13); and when the first current signal and the second current signal are greater than the first comparison value and When the value is smaller than the second comparison value, the size of the first current signal and the second current signal are continuously compared, and the minimum value is taken as the current measurement signal (S14).

In addition, when the switching state of the bridge converter 11 is hard switching, the signal measured by the current comparator 14 may cause the measured current value to be greater than the actual input current value due to the generation of the glitch. When the switching state of the bridge converter 11 is soft switching, the on-resistance of the OR field effect transistor 16 increases the current flowing through the load due to the heavy load, so that the temperature is increased, resulting in an increase in the on-resistance. The current value corresponding to the signal measured by the current measuring unit 17 is greater than the actual output current value.

Therefore, the micro processing unit 19 can also compare the magnitudes of the first current signal S1 and the second current signal S2 and take the minimum value as the current measurement signal S3. The current measurement signal S3 is the I _detect curve shown in FIG. 2B.

4A, 4B, and 4C, the fourth preferred embodiment of the micro-processing unit 19 determining the switching state of the bridge converter 11 is preset with a first difference Δ1 and a second difference Δ2. . When the first current signal S1 is greater than the second current signal S2 and the difference is greater than the first difference Δ1, the second current signal S2 is used as the current measurement signal S3. When the second current signal S2 is greater than the first current signal S1 and the difference is greater than the second difference Δ2, the first current signal S1 is used as the current measurement signal S3, and the current measurement signal is The initial state of S3 is set to be equal to the second current signal S2. The setting of the first difference Δ1 and the second difference Δ2 prevents the micro processing unit 19 from switching the current measurement signal too frequently, resulting in instability of the circuit system.

For example, as shown in FIG. 4A, the first current signal S1 is an I _CT curve, and the second current signal is an I _Oring curve. When the actual output current (I _OUT ) increases from 0, it is in an initial state. The current measurement signal S3 is equal to the second current signal S2, and the first current signal S1 is greater than the second current signal S2 and greater than the first difference Δ1, but with the actual output current (I _OUT Increasingly, the difference between the first current signal S1 and the second current signal S2 is also closer and closer, and further in turn by the second current signal S2 being greater than the first current signal S1, when the second current When the signal S2 is greater than the first current signal S1 and the difference is greater than the second difference Δ2, the current measurement signal S3 is equal to the first current signal S1. It can be seen from the above that when the actual output current (I _OUT ) increases from 0 to the maximum value, the variation curve of the current measurement signal S3 is as shown by the I _detect1 curve in FIG. 4B. Similarly, when the actual output current (I _OUT ) is reduced from the maximum value to 0, the variation curve of the current measurement signal S3 is as shown in the I _{detect 2} curve in FIG. 4C.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention. A person skilled in the art can make some modifications or modifications to equivalent embodiments by using the above-disclosed technical contents without departing from the technical scope of the present invention. It is still within the scope of the technical solution of the present invention to make any simple modifications, equivalent changes and modifications to the above embodiments.

10‧‧‧Power supply with current correction function
11‧‧‧Bridge converter
111‧‧‧DC input
112‧‧‧AC output
12‧‧‧Transformers
121‧‧‧First side
122‧‧‧second side
13‧‧‧Rectifier
131‧‧‧AC input
132‧‧‧DC output
14‧‧‧ Comparator
15‧‧‧First adjustment unit
16‧‧‧ or field effect transistor
17‧‧‧ Current measuring unit
18‧‧‧Second adjustment unit
19‧‧‧Microprocessing unit
191‧‧‧Control unit
20‧‧‧Power supply
21‧‧‧ current comparator
22‧‧‧Bridge converter

1 is a block diagram of a circuit in accordance with a preferred embodiment of the present invention. 2A, 2B and 2C are graphs showing the relationship between the current measuring signal and the output current value of the preferred embodiment of the present invention. 3 is a flow chart showing the switching state of the bridge converter in the preferred embodiment of the present invention. 4A, 4B, and 4C are graphs showing the relationship between the current measurement signal and the output current value of the preferred embodiment of the present invention. Fig. 5 is a circuit block diagram of a conventional power supply current detecting circuit.

10‧‧‧Power supply with current correction function

11‧‧‧Bridge converter

111‧‧‧DC input

112‧‧‧AC output

12‧‧‧Transformers

121‧‧‧First side

122‧‧‧second side

13‧‧‧Rectifier

131‧‧‧AC input

132‧‧‧DC output

14‧‧‧ Comparator

15‧‧‧First adjustment unit

16‧‧‧ or field effect transistor

17‧‧‧ Current measuring unit

18‧‧‧Second adjustment unit

19‧‧‧Microprocessing unit

191‧‧‧Control unit

Claims (8)

A power supply with current correction function includes: a bridge converter having a DC input terminal and an AC output terminal; a transformer having a primary side and a secondary side, the primary side system being connected to An AC output end of the bridge converter; a rectifier having an AC input end and a DC output end connected to the secondary side of the transformer; a Current Transformer connected to a DC input terminal of the bridge converter for detecting an input current of the bridge converter and outputting an input current signal; a first adjusting unit connected to the current comparator to receive the input current signal The first current signal is output by multiplying the input current signal by a first rate and a first compensation value; and an ORing FET is connected to the DC output of the rectifier. a current measuring unit is connected in parallel with the OR field effect transistor to detect the output current of the rectifier according to the voltage across the OR field and output an output current signal a second adjusting unit is connected to the current measuring unit to receive the output current signal, and multiply the output current signal by a second multiple rate and a second compensation value to output a second current signal; a micro processing unit is connected to the first adjusting unit and the second adjusting unit to receive the first current signal and the second current signal, and accordingly generate a current measuring signal; wherein the microprocessor is Presetting a first current interval and a second current interval, wherein the current value corresponding to the first current interval is smaller than a current value corresponding to the second current region, and when the first current signal or the second current signal is When the corresponding current value falls in the first current interval, the current measurement signal, etc. And in the second current signal, when the current value corresponding to the first current signal or the second current signal falls within the second current interval, the current measurement signal is equal to the first current signal. The power supply device with current correction function according to claim 1, wherein the micro processing unit presets a threshold value, and the current value corresponding to the first current interval is less than the threshold value, and the second current interval corresponds to The current value is greater than or equal to the threshold. The power supply device with current correction function according to claim 1, wherein the micro processing unit further presets a first comparison value and a second comparison value and a third current interval; the first comparison value is smaller than the a second comparison value; the current value corresponding to the first current interval is smaller than the first comparison value; the current value corresponding to the second current interval is greater than the second comparison value; and the current corresponding to the third current interval The value is between the first comparison value and the second comparison value; when the current value corresponding to the first current signal or the second current signal falls within the third current interval, the first comparison is continuously performed. The current value corresponding to the current signal and the current value corresponding to the second current signal, and the minimum value is taken as the current value corresponding to the current measurement signal. The power supply with current correction function according to any one of claims 1 to 3, wherein the bridge converter is a phase shift full bridge converter or a half bridge converter. A power supply with current correction function includes: a bridge converter having a DC input terminal and an AC output terminal; a transformer having a primary side and a secondary side, the primary side system being connected to An AC output end of the bridge converter; a rectifier having an AC input end and a DC output end, the AC input end being connected to a secondary side of the transformer; a current transformer (Current Transformer) is connected to the DC input of the bridge converter to detect the input current of the bridge converter and output an input current signal; a first adjustment unit is connected to the After receiving the input current signal, the current comparator multiplies the input current signal by a first multiple rate and adds a first compensation value to output a first current signal; or an operational field effect transistor (Oring) FET) is connected to the DC output end of the rectifier; a current measuring unit is connected in parallel with the OR field effect transistor to detect the output current of the rectifier according to the voltage across the OR field effect transistor; And outputting an output current signal; a second adjusting unit is connected to the current measuring unit to receive the output current signal, and multiplying the output current signal by a second multiple and adding a second compensation value And outputting a second current signal; a micro processing unit is connected to the first adjusting unit and the second adjusting unit to receive the first current signal and the second current signal, and generate a Measuring the signal; wherein the micro processing unit presets a first difference and a second difference; when the current value corresponding to the first current signal is greater than a current value corresponding to the second current signal, and the difference When the first difference is greater than the first current signal, the current value corresponding to the second current signal is greater than the current value corresponding to the first current signal, and the difference is greater than the second When the difference is, the current measurement signal is equal to the second current signal. The power supply with current correction function according to claim 5, wherein the bridge converter is a phase shift full bridge converter or a half bridge converter. A power supply with current correction function includes: a bridge converter having a DC input terminal and an AC output terminal; a transformer having a primary side and a secondary side, the primary side system being connected to The AC output of the bridge converter; a rectifier having an AC input terminal and a DC output terminal connected to the secondary side of the transformer; a Current Transformer connected to the DC input terminal of the bridge converter The input current of the bridge converter is detected, and an input current signal is output; a first adjusting unit is connected to the current comparator to receive the input current signal, and then multiply the input current signal by a first After the magnification and the first compensation value are adjusted, a first current signal is output; an ORing FET is connected to the DC output of the rectifier; and a current measuring unit is coupled to the Or the field effect transistor is connected in parallel to detect the output current of the rectifier according to the voltage across the OR field, and output an output current signal; a second adjustment unit is connected to the current measuring unit, Receiving the output current signal, multiplying the output current signal by a second multiple rate and adding a second compensation value, and outputting a second current signal; a micro processing unit is connected to the first The unit and the second adjusting unit receive the first current signal and the second current signal, and generate a current measuring signal; wherein the micro processing unit continuously compares the first current signal The current value and the current value corresponding to the second current signal are taken as the current value corresponding to the current measurement signal. The power supply with current correction function according to claim 7, wherein the bridge converter is a phase shift full bridge converter or a half bridge converter.