CN102611296A - Switch switching-off triggering circuit and power factor correction circuit - Google Patents

Abstract

The invention discloses a switch turn-off trigger circuit and a power factor correction circuit, which relate to the field of power electronics. The actual inductance current of the power factor correction circuit is consistent when the switch is turned off under different input voltages, thereby reducing THD and improving efficiency. The trigger circuit for turning off the switch includes: a given negative current circuit, a current feedback circuit and a comparator, the given negative current circuit generates a preset given negative current; the current feedback circuit converts the inductor current of the power factor correction circuit Feedback to the comparator; the comparator, when the inductor current of the power factor correction circuit is equal to the given negative current, generates a trigger signal that triggers the switch to be turned off; the given negative current input to the comparator or the inductor current that is electrically fed back to the comparator , a compensation signal related to the input voltage is superimposed, so that the output trigger signal varies with the input voltage, so that the inductance current on the power factor correction circuit is consistent when the trigger switch is turned off under different input voltages.

Description

Switch turn-off trigger circuit and power factor correction circuit

technical field

The invention relates to the field of power electronics, in particular to a switch turn-off trigger circuit and a power factor correction circuit.

Background technique

The application of power electronic devices is becoming more and more extensive, and the problems of harmonics and reactive power are becoming more and more serious. One of the main ways to solve this problem is to use power factor correction (PowerFactor Correct, PFC) technology. This technology is to add an active switch to the traditional rectifier circuit, and force the input current to change with the input voltage by controlling the on-off of the active switch, so as to obtain an input current close to a sine wave and a power factor close to 1.

The power factor correction circuit shown in Figure 1, in the positive half cycle of the sinusoidal alternating input voltage, the working process of the circuit is as follows:

The Q2 tube is turned on to store energy in the inductor. After the Q2 tube is turned off, the current naturally continues to flow through the diode connected in parallel with the Q1 tube. The Q1 tube is turned on to realize the zero voltage switch (Zero Voltage Switch, ZVS); When the reverse current is detected to reach a given negative current (for example -2A), the Q1 tube is turned off; the capacitor C2 is discharged to 0V, and the Q2 tube is turned on to realize ZVS. The final inductor current is shown in Figure 2 It shows that the current peak envelope is a sine wave, and then the input current close to the sine wave is obtained after filtering. Among them, the turn-off control part of the active switch Q1 tube and Q2 tube mainly includes a comparator, one input terminal of the comparator inputs a given negative current (for example -2A), and the other input terminal of the comparator inputs the feedback inductor current , when it is detected that the feedback inductor current reaches a given negative current (eg -2A), the comparator generates a shutdown signal to turn off the Q1 or Q2 tube.

There are at least the following problems in the prior art:

In the existing switching tube turn-off trigger circuit, there is a delay from the detection of -2A to the turn-off of Q1. This period of time will cause an additional increase in the negative current of the correction circuit, and the higher the input voltage, the smaller the increased negative current ΔI. The result The additional negative current ΔI is small under high input voltage, and the additional negative current ΔI is large under low input voltage; similarly, in the negative half cycle of the sinusoidal alternating input voltage, the Q2 tube also has a similar problem, and the result is turned off in different input voltage segments When the Q1 tube or Q2 tube is used, the actual negative current obtained is not consistent, which affects the total harmonic distortion (Total Harmonic Distortion, THD) and efficiency of the circuit.

Contents of the invention

The technical problem to be solved by the present invention is to provide a switch turn-off trigger circuit and a power factor correction circuit, which can make the actual negative current of the inductor obtained by the power factor correction circuit under different input voltages consistent, reduce THD, and improve power factor the efficiency of the correction circuit.

In order to achieve the above object, embodiments of the present invention adopt the following technical solutions:

A switch turn-off trigger circuit for a power factor correction circuit, comprising: a given negative current circuit, a current feedback circuit and a comparator,

The given negative current circuit is used to generate a preset given negative current, which is input to the comparator, and the given negative current is a preset current value for controlling the switch to be turned off;

The current feedback circuit is used to feed back the inductor current of the power factor correction circuit to the comparator;

The comparator is configured to generate a trigger signal to trigger the switch to be turned off when the inductor current of the power factor correction circuit is equal to the given negative current;

A given negative current input to the comparator or an inductor current fed back to the comparator is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, and the compensation signal is used to compensate the inductor current Under different input voltages, the trigger signal output by the comparator changes with the input voltage due to the different current values additionally added by the turn-off delay of the switch, so that under different input voltages , when the trigger signal triggers the switch to be turned off, the inductor currents on the power factor correction circuit are consistent.

In the switch turn-off trigger circuit and power factor correction circuit provided by the embodiments of the present invention, in the switch turn-off trigger circuit, the given negative current output by the given negative current circuit or the inductor current fed back to the comparator by the current feedback circuit is superimposed with The compensation signal that changes with the input voltage enables the trigger signal output by the switch-off trigger circuit to be dynamically adjusted according to the input voltage of the power factor correction circuit, and finally makes the power factor correction circuit on the power factor correction circuit when the switch is turned off under different input voltages The inductor currents are consistent, reducing THD and improving the efficiency of the correction circuit.

Description of drawings

FIG. 1 is a schematic diagram of a power factor correction circuit in the prior art;

2 is a schematic diagram of an inductor current of a power factor correction circuit in the prior art;

FIG. 3 is a schematic diagram of a switch turn-off trigger circuit in an embodiment of the present invention;

FIG. 4 is a schematic diagram of a switch turn-off trigger circuit in Embodiment 1 of the present invention;

FIG. 5 is a schematic structural diagram of the switch-off trigger circuit shown in FIG. 4;

FIG. 6 is a schematic diagram of a switch turn-off trigger circuit in Embodiment 2 of the present invention;

FIG. 7 is a schematic diagram of a switch turn-off trigger circuit in Embodiment 3 of the present invention.

Explanation of reference signs

11-comparator, 12-given negative current circuit, 13-current feedback circuit;

121-constant negative current module, 122-the first compensation module;

131 - current feedback module, 132 - second compensation module.

Detailed ways

An embodiment of the present invention provides a switch turn-off trigger circuit and a power factor correction circuit, so that the power factor correction circuit has the same inductor current when the switch is turned off under different input voltages, reduces THD, and improves the efficiency of the power factor correction circuit .

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. The specific embodiments described here are only used to explain the present invention, and are not intended to limit the present invention.

An embodiment of the present invention provides a switch turn-off trigger circuit for a power factor correction circuit, as shown in FIG. 3 , the circuit includes a comparator 11 , a given negative current circuit 12 and a current feedback circuit 13 ,

The given negative current circuit 12 is used to generate a preset given negative current, which is input to the comparator 11, and the given negative current is a preset current value for controlling the switch to be turned off;

A current feedback circuit 13, configured to feed back the inductor current of the power factor correction circuit to the comparator 11;

The comparator 11 is used to generate a trigger signal that triggers the switch to be turned off when the inductor current of the power factor correction circuit is equal to a given negative current;

A given negative current input to the comparator 11 or an inductor current fed back to the comparator 11 is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, and the compensation signal is used to compensate the inductor current at different input voltages Due to the different current values additionally added by the switch turn-off delay, the trigger signal output by the comparator 11 changes with the input voltage of the power factor correction circuit, so that under different input voltages, when the trigger signal triggers the switch to turn off, The inductor current across the power factor correction circuit is all the same.

Wherein, the input voltage mentioned in the present invention refers to the input voltage of the power factor correction circuit. The inductance current on the power factor correction circuit refers to the current flowing through the inductance device on the power factor correction circuit, and the inductance current is the input current of the power factor correction circuit after filtering.

There are many ways to obtain the compensation signal, and many signals can be used to realize it, as long as these signals contain the information of the AC input voltage, such as AC voltage sampling, the driving signal of the switch, and so on.

In the switch turn-off trigger circuit provided by the embodiment of the present invention, the signal output by the given negative current circuit or the signal output by the current feedback circuit is superimposed with a compensation signal, and the compensation signal contains input voltage information, which varies with the input voltage, so that the switch turn-off trigger The trigger signal output by the circuit can change dynamically with different input voltages, and finally make the inductance current on the power factor correction circuit consistent when the switch is turned off under different input voltages, reduce THD, and improve the efficiency of the correction circuit.

Embodiment one

An embodiment of the present invention provides a switch turn-off trigger circuit for a power factor correction circuit, as shown in FIG. 4 , the circuit includes:

Given the negative current circuit 12, the current feedback circuit 13 and the comparator 11, the comparator 11 is used to generate a trigger signal to trigger the switch to be turned off when the inductor current of the power factor correction circuit is equal to the given negative current;

When the given negative current input to the comparator 11 is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, the given negative current circuit 12 includes:

A constant negative current module 121 for generating a preset given negative current, the constant negative current module outputs a constant given negative current;

A first compensation module 122 for outputting the first compensation signal, the first compensation signal is related to the input voltage, when the input voltage is high, the first compensation signal is large, and when the input voltage When low, the first compensation signal is small;

The first compensation signal output by the first compensation module 122 is superimposed on the constant given negative current output by the constant negative current module 121 and input to the comparator 11 .

The current feedback circuit 13 in this embodiment is used to feed back the inductor current of the power factor correction circuit, and the constant negative current module 121 is used to generate a constant negative current (for example -2A), which can be easily realized by those skilled in the art. And there are various ways to implement it, which will not be repeated here.

The first compensation module 122 is used to output the first compensation signal. The characteristic of the first compensation signal is related to the input voltage. When the input voltage is high, the first compensation signal is large; when the input voltage is low, the first compensation signal is small, and finally The total given negative current input to the comparator 11 for controlling the switch to turn off is large when the input voltage is high and small when the input voltage is low.

There are various specific circuits and signals for realizing the first compensation module 122 . Wherein, optionally, the signal used to realize the function of the first compensation module 122 includes the duty cycle information of the AC input voltage, the duty cycle is large when the input voltage is high, and the duty cycle is small when the input voltage is low, such as AC voltage sampling, switch drive signal, etc.

Figure 5 shows a specific switch off trigger circuit, the circuit includes: a comparator 11, a given negative current circuit 12 and a current feedback circuit, the given negative current circuit 12 includes: a constant negative current module 121 and a first compensation module 122;

Wherein, the first compensation module 122 includes a low-pass filter, and the input terminal of the low-pass filter inputs the high-frequency driving signal PWM2B of the switch. Here, the signal input to the input terminal of the low-pass filter is not limited to the high-frequency drive signal PWM2B, and may also be an AC voltage sampling signal, as long as it has a large duty cycle when the input voltage is high and a small duty cycle when the input voltage is low. Features are fine. The input signal of the low-pass filter has a large duty cycle when the input voltage is high, and a small duty cycle when the input voltage is low. After filtering, a large negative current is obtained at a high input voltage, and a small negative current is obtained at a low input voltage.

Due to the switch off delay, the ΔI of the additional increase in the negative inductor current is inconsistent under different input voltages (the ΔI is small at high input voltage, and the ΔI is large at low input voltage). The total given negative current signal of the device presents the characteristics that it is large at high input voltage and small at low input voltage. As a result, the trigger signal for controlling the switch to turn off varies with the input voltage. Therefore, compared with the existing technology, ΔI will become larger under high input voltage, and ΔI will become smaller under low input voltage, so that the inductor current obtained by the power factor correction circuit when the switch is turned off is relatively consistent, and the filter is more accurate. Close to sine wave, reduce THD, improve power factor correction circuit efficiency. By continuously optimizing the parameter values of the components that make up the first compensation module, the specific first compensation signal output by the first compensation module 122 is superimposed on the constant signal generated by the constant negative current module 121, and input to the input terminal of the comparator 11, namely Pin 4 of comparator 11 in Fig. 5. When the comparator generates a trigger signal based on the input negative current signal and the feedback inductor current to turn off the switch, the power factor correction circuit obtains the same inductor current when the switch is turned off, so that the filtered current is closer to a sine wave , reduce THD, improve power factor correction circuit efficiency.

Embodiment two

The embodiment of the present invention also provides a switch turn-off trigger circuit for a power factor correction circuit, as shown in FIG. 6 , the circuit includes:

Comparator 11, given negative current circuit 12 and current feedback circuit,

The comparator 11 is used to generate a trigger signal that triggers the switch to be turned off when the inductor current of the power factor correction circuit is equal to a given negative current;

a current feedback circuit, for feeding back the inductor current of the power factor correction circuit to the comparator;

When the given negative current input to the comparator 11 is superimposed with the compensation signal related to the input voltage of the power factor correction circuit, the given negative current circuit 12 includes: a digital signal processor and a filter, and the output of the digital signal processor is related to the The high-frequency carrier signal related to the input voltage is filtered by the filter and then input to the input terminal of the comparator 11, that is, pin 4 of the comparator 11 in FIG. 6 . The high-frequency carrier signal includes duty cycle information of the input voltage, and the high-frequency carrier signal has a large duty cycle when the input voltage is high, and a small duty cycle when the input voltage is low.

Optionally, the digital signal processor in FIG. 6 can also be other PWM generators for sending out high-frequency carrier signals related to the input voltage.

The input signal of the digital signal processor in this embodiment can be selected from many kinds, as long as these signals include the information of the AC input voltage, such as AC voltage sampling, the driving signal of the switch tube, etc., the digital signal in this embodiment The output signal of the processor contains the duty cycle information of the AC input voltage, the duty cycle is small when the input voltage is high, and the duty cycle is large when the input voltage is low.

The duty ratio of the output signal in this embodiment is small when the input is high voltage, and the duty ratio is large when the input is low voltage. In this way, after filtering, a large given negative current is obtained under high voltage, and a small given negative current is obtained under low voltage. Finally, Make the inductor current obtained by the power factor correction circuit consistent when the switch is turned off, make the input current closer to the sine wave, reduce THD, and improve the efficiency of the power factor correction circuit.

Embodiment Three

As shown in FIG. 7, the embodiment of the present invention also provides a switch turn-off trigger circuit for a power factor correction circuit, including: a comparator 11, a given negative current circuit 12 and a current feedback circuit 13, wherein the feedback to the comparison When the inductor current of the device 11 is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, the current feedback circuit 13 includes:

A current feedback module 131 for feeding back the inductor current of the power factor correction circuit to the comparator;

A second compensation module 132 for outputting the second compensation signal, the second compensation signal is related to the input voltage, when the input voltage is high, the second compensation signal is small, and the input voltage When low, the second compensation signal is large;

The second compensation signal output by the second compensation module 132 is superimposed on the signal output by the current feedback module 131 , and then input to the comparator 11 .

The second compensation module 132 outputs a compensation signal that varies with the input voltage. Wherein, the input voltage in this embodiment refers to the inductor current of the power factor correction circuit, and the characteristic of the second compensation signal is that the second compensation signal is small when the input voltage is high, and the second compensation signal is large when the input voltage is low.

In this embodiment, the given negative current circuit 12 is used to generate a constant given negative current, and the current feedback module 131 in the current feedback circuit 13 is used to output the feedback inductance current signal, which can be easily realized by those skilled in the art. Moreover, there are various implementation methods, which will not be described one by one here.

There are various specific circuits and signals for realizing the second compensation module 132 . Wherein, optionally, a specific implementation scheme of the second compensation module 132 is to use a signal with a small duty cycle when the input voltage is high and a high duty cycle signal when the input voltage is low, and obtain a signal with a corresponding input voltage after filtering by a filter. The changing second compensation signal is characterized by a small second compensation signal under high input voltage and a large second compensation signal under low input voltage. The second compensation signal is superimposed on the current feedback signal output by the current feedback module 131 and input to the input terminal of the comparator 11. In this way, although the given negative current is constant, the second compensation signal is superimposed on the inductor current fed back to the comparator 11 , the trigger signal generated by the comparator 11 will still change with the input voltage, and finally make the inductor current obtained by the power factor correction circuit consistent when the switch is turned off, make the input current closer to a sine wave, reduce THD, and improve the efficiency of the power factor correction circuit.

Embodiment Four

An embodiment of the present invention further provides a power factor correction circuit, comprising: the switch turn-off trigger circuit described in any one of the above embodiments.

In the power factor correction circuit provided by the embodiment of the present invention, the given negative current signal or current feedback signal for controlling the turn-off of the active switch is superimposed with a compensation signal that changes with the input voltage, so that the trigger signal output by the switch turn-off trigger circuit can be It changes dynamically with different input voltages, and finally makes the inductor current on the power factor correction circuit consistent when the switch is turned off under different input voltages, reduces THD, and improves the efficiency of the correction circuit.

The above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Anyone skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present invention. Should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (6)

1. A switch turn-off trigger circuit for a power factor correction circuit, comprising: a given negative current circuit, a current feedback circuit and a comparator, The given negative current circuit is used to generate a preset given negative current, which is input to the comparator, and the given negative current is a preset current value for controlling the switch to be turned off; The current feedback circuit is used to feed back the inductor current of the power factor correction circuit to the comparator; The comparator is configured to generate a trigger signal to trigger the switch to be turned off when the inductor current of the power factor correction circuit is equal to the given negative current; It is characterized in that the given negative current input to the comparator or the inductor current fed back to the comparator is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, and the compensation signal is used to compensate The different current values of the inductor current that are additionally increased due to the turn-off delay of the switch under different input voltages make the trigger signal output by the comparator vary with the input voltage, so that Under the input voltage, when the trigger signal triggers the switch to be turned off, the inductor currents on the power factor correction circuit are consistent. 2. The circuit of claim 1, wherein When the given negative current input to the comparator is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, the given negative current circuit includes: A constant negative current module for generating a preset given negative current, the constant negative current module outputs a constant given negative current; A first compensation module for outputting a first compensation signal, the first compensation signal is related to the input voltage, when the input voltage is high, the first compensation signal is large, and when the input voltage is low, The first compensation signal is small; The first compensation signal output by the first compensation module is superimposed on the constant given negative current output by the constant negative current module, and input to the comparator. 3 . The circuit according to claim 2 , wherein the first compensation module comprises a low-pass filter, and an input terminal of the low-pass filter inputs a high-frequency driving signal of the switch. 4 . 4. The circuit according to claim 1, wherein when the given negative current input to the comparator is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, the given The negative current circuit includes a digital signal processor and a filter. The digital signal processor outputs a high-frequency carrier signal related to the input voltage, which is filtered by the filter and then input to the comparator. The high-frequency carrier signal The duty cycle information of the input voltage is included, and the high frequency carrier signal has a large duty cycle when the input voltage is high, and a small duty cycle when the input voltage is low. 5. The circuit of claim 1, wherein When the current fed back to the comparator is superimposed with a compensation signal related to the input voltage of the power factor correction circuit, the current feedback circuit includes: A current feedback module for feeding back the inductor current of the power factor correction circuit to the comparator; A second compensation module for outputting a second compensation signal, the second compensation signal is related to the input voltage, when the input voltage is high, the second compensation signal is small, and when the input voltage is low, The second compensation signal is large; The second compensation signal output by the second compensation module is superimposed on the signal output by the current feedback module, and input to the comparator. 6. A power factor correction circuit, comprising: the switch turn-off trigger circuit according to any one of claims 1 to 5.

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