Method and circuit for balancing valley breakover current

Abstract

The invention provides a method and a circuit for balancing valley breakover current, and relates to the field of switching power supplies, the circuit comprises an input end electrically connected with a collector of a switching tube, an output end electrically connected with an emitter of the switching tube, an input sampling unit used for sampling input voltage, a controller used for valley detection of the input voltage, and an output sampling unit used for outputting the valley breakover current. The output sampling unit is used for sampling the output voltage, and the rising and falling edge judgment unit is used for determining the change trend of the input voltage according to the output of the input sampling unit; the threshold switching unit is used for switching the upper threshold and the lower threshold of the comparator according to the change trend of the input voltage; the comparator is electrically connected with the output end of the output sampling unit and is used for outputting a comparison signal based on the variation trend of the output voltage, the output voltage, an upper threshold and a lower threshold; and the controller is also used for controlling the state of the switching tube based on the valley bottom detection result and the comparison signal, and has the advantage of balancing the valley bottom conduction current of the switching power supply.

Description

Technical Field

[0001] The present invention relates to the field of switching power supplies, and in particular to a method and a circuit for balancing valley conduction current. Background Art

[0002] A switching power supply (SMPS) is a highly efficient power conversion device that controls and stabilizes the output voltage by rapidly switching electronic components (such as transistors). Figure 1 is a circuit diagram of a valley-conduction switching power supply in the prior art, such as Figure 1 As shown in the figure, the switching power supply uses the switching circuit and feedback control technology to achieve stable control of the output voltage through high-frequency switching and adjusting the duty cycle of the switch, as well as the adjustment of the feedback loop. Specifically, the switching power supply contains a feedback loop to monitor the output voltage and adjust it. Usually, a comparator is used to compare the difference between the set output voltage value and the actual output voltage value, and the switching frequency and duty cycle of the switch tube are adjusted according to the size of the difference to achieve a stable output voltage. Figure 2 Schematic diagram of the corresponding relationship between the input voltage and the output level of the comparator of the valley-conducting switching power supply in the prior art, such as Figure 2 As shown, in the prior art, in order to avoid repeated flipping of the comparator output, the hysteresis of the comparator is set, that is, two different threshold voltages are set, namely, the upper threshold U+ and the lower threshold U-. The difference between the two thresholds is called the hysteresis ΔU=U+-U-. When the input voltage of the comparator changes from large to small, it corresponds to the lower threshold U-. When the input voltage of the comparator changes from small to large, it corresponds to the upper threshold U+. In the switching power supply with valley conduction, in order to reduce switching loss and improve efficiency, the switch tube is only allowed to be turned on when the source-drain voltage of the switch tube reaches the lowest valley, that is, the switch tube can only be turned on when the source-drain voltage of the switch tube is lower than a certain threshold. Therefore, it is necessary to add a valley detection controller acting on the switch tube on the basis of the switching power supply.

[0003] Figure 3 Schematic diagram of the waveform of the input voltage, the charging current flowing through the switch tube and the output voltage of the valley conduction of the sine wave input in the prior art, such as Figure 3 As shown in the figure, due to the hysteresis of the comparator, the switch will be turned on at a smaller voltage and turned off at a larger voltage. The characteristics of the switch tube itself will cause a delay in the opening and closing of the switch tube, which aggravates the imbalance of the charging current on both sides. The current flowing through the switch tube is unbalanced between the rising and falling edges of the input voltage, and the falling current is smaller than the rising current. The imbalance of charging current will lead to the following problems: 1. The power consumption of the switch tube is too high and the efficiency becomes low; 2. The overcharging caused by the turn-off delay of the switch tube increases the output voltage ripple; 3. The excessive charging current affects electromagnetic interference.

[0004] Therefore, it is necessary to provide a method and circuit for balancing the valley conduction current, which are used to balance the valley conduction current of a switching power supply. Summary of the invention

[0005] The present invention provides a circuit for balancing valley bottom conduction current, comprising an input end, a switch tube, an output end, an output sampling unit, an input sampling unit and a controller, wherein the input end is electrically connected to the collector of the switch tube, the output end is electrically connected to the emitter of the switch tube, the input sampling unit is electrically connected to the input end and is used to sample the input voltage, the controller is used to perform valley bottom detection according to the output of the input sampling unit, the output sampling unit is electrically connected to the output end and is used to sample the output voltage, and further comprises: a rising and falling edge determination unit, used to determine the change trend of the input voltage according to the output of the input sampling unit, wherein the change trend is rising or falling; a threshold switching unit, used to switch the upper threshold and the lower threshold of the comparator according to the change trend of the input voltage; the comparator is electrically connected to the output end of the output sampling unit and is used to output a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold; the controller is also used to control the state of the switch tube based on the valley bottom detection result and the comparison signal.

[0006] Further, the threshold switching unit switches the upper threshold and lower threshold of the comparator, including: when the changing trend of the input voltage is rising, the upper threshold of the comparator is the rising upper threshold, and the lower threshold of the comparator is the rising lower threshold; when the changing trend of the input voltage is falling, the upper threshold of the comparator is the falling upper threshold, and the lower threshold of the comparator is the falling lower threshold, wherein the rising upper threshold is smaller than the falling upper threshold.

[0007] Furthermore, the hysteresis between the rising upper threshold and the rising lower threshold is equal to the hysteresis between the falling upper threshold and the falling lower threshold.

[0008] Furthermore, the output sampling unit includes a first resistor and at least two voltage-dividing resistors which are sequentially connected in series between the output terminal and the input terminal of the comparator.

[0009] Further, the threshold switching unit includes at least one threshold switching switch, wherein at least one voltage dividing resistor is connected in parallel with the threshold switching switch.

[0010] Furthermore, the comparator outputs a comparison signal based on the changing trend of the output voltage, the output voltage, the upper threshold and the lower threshold, including: when the changing trend of the input voltage is rising and the changing trend of the output voltage is rising, the output voltage is compared with the rising upper threshold; when the changing trend of the input voltage is rising and the changing trend of the output voltage is falling, the output voltage is compared with the rising lower threshold.

[0011] Furthermore, the comparator outputs a comparison signal based on the changing trend of the output voltage, the output voltage, the upper threshold and the lower threshold, including: when the changing trend of the input voltage is decreasing and the changing trend of the output voltage is increasing, the output voltage is compared with the decreasing upper threshold; when the changing trend of the input voltage is decreasing and the changing trend of the output voltage is decreasing, the output voltage is compared with the decreasing lower threshold.

[0012] Furthermore, the controller controls the state of the switch tube based on the valley detection result and the comparison signal, including: when the comparison signal is at a high level and the input voltage is at the valley bottom, controlling the switch tube to be turned on.

[0013] The present invention provides a method for balancing valley conduction current, which is applied to the above-mentioned circuit for balancing valley conduction current, including: sampling input voltage; sampling output voltage; determining the change trend of the input voltage according to the sampled input voltage, wherein the change trend is rising or falling; switching the upper threshold and the lower threshold of the comparator according to the change trend of the input voltage; determining the change trend of the output voltage according to the sampled output voltage; the comparator outputs a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold; and controlling the state of the switch tube based on the valley detection result and the comparison signal.

[0014] Compared with the prior art, the method and circuit for balancing valley conduction current provided by the present invention have at least the following beneficial effects:

[0015] 1. Improve energy efficiency: By precisely controlling the conduction timing of the switch tube (i.e. at the bottom of the input voltage), the switching loss is reduced and the energy efficiency of the circuit is improved.

[0016] 2. Stable output voltage: The dynamic threshold switching mechanism can adjust the upper and lower thresholds of the comparator according to the changing trend of the input voltage, thereby maintaining the stability of the output voltage under different input conditions.

[0017] 3. Strong adaptability: It can automatically adapt to the rising and falling trends of the input voltage, and achieve precise adjustment of the output voltage through intelligent threshold switching and comparison control.

[0018] 4. Reduce electromagnetic interference: Since the switch tube is turned on at the bottom of the input voltage, the current impact and electromagnetic interference during the switching action are reduced, and the electromagnetic compatibility of the circuit is improved.

[0019] 5. Extend service life: Precise switching control reduces the switching frequency and switching loss of the switch tube, thereby extending the service life of the switch tube and the entire circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0021] Figure 1 It is a circuit diagram of a valley-conduction switching power supply in the prior art;

[0022] Figure 2 It is a schematic diagram of the corresponding relationship between the input voltage and the output level of the comparator of the valley-conduction switching power supply in the prior art;

[0023] Figure 3 It is a waveform diagram of the input voltage, the charging current flowing through the switch tube and the output voltage of the valley conduction of the sine wave input in the prior art;

[0024] Figure 4 is a circuit diagram of a circuit for balancing valley conduction current shown in some embodiments of this specification;

[0025] Figure 5 A schematic diagram of waveforms of an input voltage, a charging current flowing through a switch tube, and an output voltage of a circuit for balancing valley conduction current shown in some embodiments of this specification;

[0026] Figure 6 A schematic flow chart of a method for balancing valley conduction current shown in some embodiments of this specification. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0028] Figure 4 is a circuit diagram of a circuit for balancing valley conduction current shown in some embodiments of this specification, such as Figure 4 As shown, a circuit for balancing valley bottom conduction current includes an input end, a switch tube, an output end, an output sampling unit, an input sampling unit and a controller. The input end is electrically connected to the collector of the switch tube, the output end is electrically connected to the emitter of the switch tube, the input sampling unit is electrically connected to the input end for sampling the input voltage, the controller is used to perform valley bottom detection according to the output of the input sampling unit, and the output sampling unit is electrically connected to the output end for sampling the output voltage.

[0029] Specifically, the output sampling unit and the output sampling unit can be implemented by a voltage sensor or a voltage divider circuit.

[0030] like Figure 4 As shown, a circuit for balancing valley conduction current also includes:

[0031] A rising and falling edge determination unit, used to determine a change trend of the input voltage according to the output of the input sampling unit, wherein the change trend is rising or falling;

[0032] A threshold switching unit, used to switch the upper threshold and the lower threshold of the comparator according to the change trend of the input voltage;

[0033] A comparator, electrically connected to the output terminal of the output sampling unit, for outputting a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold;

[0034] The controller is also used to control the state of the switch tube based on the valley detection result and the comparison signal.

[0035] Specifically, the threshold switching unit switches the upper threshold and the lower threshold of the comparator, including:

[0036] When the input voltage changes in an upward trend, the upper threshold of the comparator is the rising upper threshold, and the lower threshold of the comparator is the rising lower threshold;

[0037] When the input voltage changes in a downward trend, the upper threshold of the comparator is the falling upper threshold, and the lower threshold of the comparator is the falling lower threshold, wherein the rising upper threshold is less than the falling upper threshold. The hysteresis between the rising upper threshold and the rising lower threshold is equal to the hysteresis between the falling upper threshold and the falling lower threshold.

[0038] In some embodiments, the output sampling unit includes a first resistor and at least two voltage-dividing resistors connected in series between the output terminal and the input terminal of the comparator. The threshold switching unit includes at least one threshold switching switch, wherein at least one voltage-dividing resistor is connected in parallel with the threshold switching switch. The controller can be used to control the switching state of the threshold switching switch, and by controlling the switching state of the threshold switching switch, the ratio of the sampling voltage is changed, thereby realizing the threshold switching of the comparator.

[0039] In some embodiments, the rising and falling edge determination unit can sample the input voltage through an ADC (analog-to-digital converter) and store the sampling results in a memory. A new sampling value is obtained in each sampling cycle. The current sampling value is compared with the previous sampling value. If the current sampling value is greater than the previous sampling value, it is judged that the input voltage is on an upward trend; if the current sampling value is less than the previous sampling value, it is judged that the input voltage is on a downward trend. In order to reduce the impact of noise and interference on the judgment result, the sampling value can be smoothed. For example, a moving average filter or an exponential smoothing filter can be used to smooth the sampling value.

[0040] In some embodiments, the comparator outputs a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold, including:

[0041] When the input voltage trend is rising and the output voltage trend is rising, the output voltage is compared with the rising upper threshold;

[0042] When the input voltage trend is rising and the output voltage trend is falling, the output voltage is compared with the rising lower threshold;

[0043] When the input voltage trend is decreasing and the output voltage trend is increasing, the output voltage is compared with the decreasing upper threshold;

[0044] When the input voltage changes in a decreasing trend and the output voltage changes in a decreasing trend, the output voltage is compared with a decreasing lower threshold.

[0045] In some embodiments, the controller controls the state of the switch tube based on the valley detection result and the comparison signal, including: when the comparison signal is at a high level and the input voltage is at the valley bottom, controlling the switch tube to turn on.

[0046] Figure 5 A schematic diagram of waveforms of an input voltage, a charging current flowing through a switch tube, and an output voltage of a circuit for balancing valley conduction current shown in some embodiments of this specification, such as Figure 5 As shown in the figure, in a circuit that balances the valley conduction current, the switch tube will turn on at the falling edge of the input voltage and turn off at the rising edge, that is, the switch is turned on at the falling lower threshold of the falling edge and turned off at the rising upper threshold of the rising edge. The values ​​of the falling lower threshold and the rising upper threshold can be adjusted according to demand, so that the falling lower threshold is greater than the rising upper threshold, achieving the anti-hysteresis effect of the switch. The anti-hysteresis simultaneously offsets the original hysteresis and the overcharge caused by the switch delay.

[0047] Figure 6 A flow chart of a method for balancing valley conduction current shown in some embodiments of this specification is as follows: Figure 6As shown, a method for balancing valley conduction current may include the following steps.

[0048] Sample input voltage;

[0049] Sample output voltage;

[0050] Determine a change trend of the input voltage according to the sampled input voltage, wherein the change trend is an increase or a decrease;

[0051] According to the changing trend of the input voltage, the upper threshold and the lower threshold of the comparator are switched;

[0052] According to the sampled output voltage, determine the change trend of the output voltage;

[0053] The comparator outputs a comparison signal based on the changing trend of the output voltage, the output voltage, the upper threshold and the lower threshold;

[0054] Based on the valley detection result and the comparison signal, the state of the switch tube is controlled.

[0055] A method for balancing valley conduction current can be applied to the above-mentioned circuit for balancing valley conduction current. For more description, please refer to the relevant description of a circuit for balancing valley conduction current, which will not be repeated here.

[0056] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A circuit for balancing valley bottom conduction current, comprising an input end, a switch tube, an output end, an output sampling unit, an input sampling unit and a controller, wherein the input end is electrically connected to the collector of the switch tube, the output end is electrically connected to the emitter of the switch tube, the input sampling unit is electrically connected to the input end for sampling input voltage, the controller is used to perform valley bottom detection according to the output of the input sampling unit, the output sampling unit is electrically connected to the output end for sampling output voltage, and is characterized in that: Also includes: A rising and falling edge determination unit, used to determine a change trend of the input voltage according to the output of the input sampling unit, wherein the change trend is rising or falling; A threshold switching unit, used to switch the upper threshold and the lower threshold of the comparator according to the change trend of the input voltage; A comparator, electrically connected to the output end of the output sampling unit, for outputting a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold; The controller is also used to control the state of the switch tube based on the valley detection result and the comparison signal.

2. A circuit for balancing valley conduction current according to claim 1, characterized in that: The threshold switching unit switches the upper threshold and the lower threshold of the comparator, including: When the input voltage changes in an upward trend, the upper threshold of the comparator is the rising upper threshold, and the lower threshold of the comparator is the rising lower threshold; When the input voltage changes in a decreasing trend, the upper threshold of the comparator is a decreasing upper threshold, and the lower threshold of the comparator is a decreasing lower threshold, wherein the increasing upper threshold is smaller than the decreasing upper threshold.

3. A circuit for balancing valley conduction current according to claim 2, characterized in that: The hysteresis between the rising upper threshold and the rising lower threshold is equal to the hysteresis between the falling upper threshold and the falling lower threshold.

4. A circuit for balancing valley conduction current according to claim 3, characterized in that: The output sampling unit comprises a first resistor and at least two voltage dividing resistors which are sequentially connected in series between an output terminal and an input terminal of a comparator.

5. The circuit for balancing valley conduction current according to claim 5, characterized in that: The threshold switching unit includes at least one threshold switching switch, wherein at least one voltage dividing resistor is connected in parallel with the threshold switching switch.

6. A circuit for balancing valley conduction current according to claim 2 or 3, characterized in that: The comparator outputs a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold, including: When the input voltage trend is rising and the output voltage trend is rising, the output voltage is compared with the rising upper threshold; When the input voltage trend is rising and the output voltage trend is falling, the output voltage is compared with the rising lower threshold.

7. The circuit for balancing valley conduction current according to claim 6, characterized in that: The comparator outputs a comparison signal based on the change trend of the output voltage, the output voltage, the upper threshold and the lower threshold, including: When the input voltage trend is decreasing and the output voltage trend is increasing, the output voltage is compared with the decreasing upper threshold; When the input voltage changes in a decreasing trend and the output voltage changes in a decreasing trend, the output voltage is compared with a decreasing lower threshold.

8. A circuit for balancing valley current according to any one of claims 1 to 4, characterized in that: The controller controls the state of the switch tube based on the valley detection result and the comparison signal, including: When the comparison signal is at a high level and the input voltage is at the bottom, the switch tube is controlled to be turned on.

9. A method for balancing valley conduction current, applied to a circuit for balancing valley conduction current as claimed in any one of claims 1 to 8, comprising: Sample input voltage; Sample output voltage; Determine a change trend of the input voltage according to the sampled input voltage, wherein the change trend is an increase or a decrease; According to the changing trend of the input voltage, the upper threshold and the lower threshold of the comparator are switched; According to the sampled output voltage, determine the change trend of the output voltage; The comparator outputs a comparison signal based on the changing trend of the output voltage, the output voltage, the upper threshold and the lower threshold; Based on the valley detection result and the comparison signal, the state of the switch tube is controlled.

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