Circuit for balancing valley breakover current

Abstract

The utility model provides a circuit for balancing valley breakover current, which relates to the field of switching power supplies, and 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] This invention relates to the field of switching power supplies, and in particular to a circuit for balancing the conduction current at valleys. Background Technology

[0002] A switched-mode 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 This is a circuit diagram of a switching power supply with valley-level conduction in existing technology, such as... Figure 1 As shown, a switching power supply utilizes switching circuits and feedback control technology to achieve stable output voltage control through high-frequency switching, adjusting the duty cycle of the switches, and regulating the feedback loop. Specifically, the switching power supply contains an internal feedback loop for monitoring and adjusting the output voltage. Typically, 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 switching transistors are adjusted based on the magnitude of the difference to achieve a stable output voltage. Figure 2 This is a schematic diagram illustrating the correspondence between the input voltage and output level of a comparator in a valley-conducting switching power supply in existing technology, such as... Figure 2 As shown, in existing technologies, to avoid repeated toggling of the comparator output, a hysteresis is set for the comparator, i.e., two different threshold voltages are set: an upper threshold U+ and a lower threshold U-. The difference between the two thresholds is called the hysteresis ΔU = U+ - U-. When the comparator's input voltage changes from large to small, it corresponds to the lower threshold U-; when the comparator's input voltage changes from small to large, it corresponds to the upper threshold U+. In a valley-based switching power supply, to reduce switching losses and improve efficiency, the switching transistor is only allowed to conduct when its source-drain voltage reaches its lowest valley level. That is, the switching transistor can only conduct when its source-drain voltage is below a certain threshold. Therefore, a valley detection controller acting on the switching transistor needs to be added to the switching power supply.

[0003] Figure 3 This is a waveform diagram of the input voltage at the valley of a sinusoidal input, the charging current flowing through the switching transistor, and the output voltage in existing technology, such as... Figure 3 As shown, due to the comparator's hysteresis causing the switch to turn on at lower voltages and turn off at higher voltages, and the inherent characteristics of the switching transistor, there is a delay in the switching on and off. This exacerbates the imbalance in the charging current, resulting in an imbalance between the rising and falling edges of the input voltage's current, with the falling edge current being less than the rising edge current. This imbalance in the charging current leads to the following problems: 1. Excessive power consumption and reduced efficiency of the switching transistor; 2. Increased output voltage ripple due to overcharging caused by the switching transistor's turn-off delay; 3. Excessive charging current affecting electromagnetic interference.

[0004] Therefore, there is a need to provide a circuit for balancing the valley conduction current in a switching power supply. Summary of the Invention

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

[0006] Furthermore, the threshold switching unit switches the upper and lower thresholds of the comparator, including: when the input voltage trend is upward, 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 trend is downward, 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 upper rising threshold and the lower rising threshold is equal to the hysteresis between the upper falling threshold and the lower falling threshold.

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

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

[0010] Furthermore, 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 change trend of the input voltage is rising and the change trend of the output voltage is rising, comparing the output voltage with the rising upper threshold; when the change trend of the input voltage is rising and the change trend of the output voltage is falling, comparing the output voltage 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, comparing the output voltage 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, comparing the output voltage with the decreasing lower threshold.

[0012] Furthermore, the controller controls the state of the switching transistor based on the valley detection result and the comparison signal, including: when the comparison signal is high and the input voltage is at the valley, controlling the switching transistor to turn on.

[0013] Compared with existing technologies, the circuit for balancing valley current provided by this invention has at least the following beneficial effects:

[0014] 1. Improved energy efficiency: By precisely controlling the turn-on timing of the switching transistor (i.e., at the bottom of the input voltage), switching losses are reduced, thus improving the energy efficiency of the circuit.

[0015] 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.

[0016] 3. High adaptability: It can automatically adapt to the rising and falling trends of the input voltage, and achieve precise regulation of the output voltage through intelligent threshold switching and comparison control.

[0017] 4. Reduced electromagnetic interference: Since the switching transistor conducts at the bottom of the input voltage, the current surge and electromagnetic interference during switching are reduced, thus improving the electromagnetic compatibility of the circuit.

[0018] 5. Extended service life: Precise switching control reduces the switching frequency and switching losses of the switching transistor, thereby extending the service life of the switching transistor and the entire circuit. Attached Figure Description

[0019] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0020] Figure 1 This is a circuit diagram of a switching power supply that conducts through a valley in the existing technology;

[0021] Figure 2 This is a schematic diagram illustrating the correspondence between the input voltage and output level of a comparator in a switching power supply that conducts at the valley bottom in the prior art.

[0022] Figure 3This is a waveform diagram of the input voltage, the charging current flowing through the switching transistor, and the output voltage at the valley of a sinusoidal input in the existing technology.

[0023] Figure 4 This is a circuit diagram illustrating a circuit for balancing valley conduction current as shown in some embodiments of this specification.

[0024] Figure 5 This specification provides waveform diagrams of the input voltage, charging current flowing through the switching transistor, and output voltage of a circuit for balancing valley conduction current, as illustrated in some embodiments. Detailed Implementation

[0025] To more clearly illustrate the technical solutions of the embodiments in this specification, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some examples or embodiments of this specification. For those skilled in the art, these drawings can be applied to other similar scenarios without creative effort. Unless obvious from the context or otherwise specified, the same reference numerals in the drawings represent the same structures or operations.

[0026] Figure 4 This is a circuit diagram illustrating a circuit for balancing valley conduction current as shown in some embodiments of this specification, such as... Figure 4 As shown, a circuit for balancing valley current includes an input terminal, a switching transistor, an output terminal, an output sampling unit, an input sampling unit, and a controller. The input terminal is electrically connected to the collector of the switching transistor, the output terminal is electrically connected to the emitter of the switching transistor, the input sampling unit is electrically connected to the input terminal and is used to sample the input voltage, the controller is used to perform valley detection based on the output of the input sampling unit, and the output sampling unit is electrically connected to the output terminal and is used to sample the output voltage.

[0027] Specifically, the output sampling unit and the output sampling circuit can be implemented using a voltage sensor or a voltage divider circuit.

[0028] like Figure 4 As shown, a circuit for balancing valley current also includes:

[0029] The rising and falling edge determination unit is used to determine the trend of the input voltage change based on the output of the input sampling unit, wherein the trend of change is rising or falling.

[0030] The threshold switching unit is used to switch the upper and lower thresholds of the comparator according to the changing trend of the input voltage.

[0031] The comparator is electrically connected to the output terminal 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.

[0032] The controller is also used to control the state of the switching transistor based on the valley detection results and comparison signals.

[0033] Specifically, the threshold switching unit switches the upper and lower thresholds of the comparator, including:

[0034] 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.

[0035] When the input voltage trend is downward, the comparator's upper threshold is the downward upper threshold, and the comparator's lower threshold is the downward lower threshold, where the rising upper threshold is smaller than the falling upper threshold. The hysteresis between the rising upper and lower thresholds is equal to the hysteresis between the falling upper and lower thresholds.

[0036] In some embodiments, the output sampling unit includes a first resistor and at least two voltage divider 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 divider 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, thereby changing the ratio of the sampled voltage and thus realizing the threshold switching of the comparator.

[0037] In some embodiments, the rising / falling edge determination unit can sample the input voltage using an ADC (analog-to-digital converter) and store the sampling results in memory. A new sample value is acquired in each sampling cycle. The current sample value is compared with the previous sample value. If the current sample value is greater than the previous sample value, the input voltage is determined to be rising; if the current sample value is less than the previous sample value, the input voltage is determined to be falling. To reduce the impact of noise and interference on the determination result, the sampled values ​​can be smoothed. For example, a moving average filter or an exponential smoothing filter can be used to smooth the sampled values.

[0038] In some embodiments, the comparator outputs a comparison signal based on the trend of output voltage change, the output voltage, the upper threshold, and the lower threshold, including:

[0039] When both the input voltage and output voltage show an upward trend, the output voltage is compared with the upper threshold of the upward trend.

[0040] When the input voltage trend is upward and the output voltage trend is downward, the output voltage is compared with the rising lower threshold.

[0041] When the input voltage trend is decreasing and the output voltage trend is increasing, the output voltage is compared with the decreasing upper threshold.

[0042] When both the input voltage and output voltage show a decreasing trend, the output voltage is compared with the decreasing lower threshold.

[0043] In some embodiments, the controller controls the state of the switching transistor based on the valley detection result and the comparison signal, including: controlling the switching transistor to turn on when the comparison signal is high and the input voltage is at the valley.

[0044] Figure 5 This specification provides waveform diagrams of the input voltage, charging current flowing through the switching transistor, and output voltage of a circuit for balancing valley conduction current, as illustrated in some embodiments. Figure 5 As shown, in a circuit that balances the valley current, the switching transistor turns on at the falling edge of the input voltage and turns off at the rising edge. This achieves the switch turning on at the lower threshold of the falling edge and turning off at the upper threshold of the rising edge. The values ​​of the lower and upper thresholds can be adjusted as needed, making the lower threshold greater than the upper threshold, thus achieving the anti-hysteresis effect of the switch. The anti-hysteresis simultaneously cancels out the original hysteresis and the overcharge caused by the switching delay.

[0045] Finally, it should be understood that the embodiments described in this specification are merely illustrative of the principles of the embodiments described herein. Other variations may also fall within the scope of this specification. Therefore, alternative configurations of the embodiments described herein are intended to be illustrative rather than limiting, and should be considered consistent with the teachings of this specification. Accordingly, the embodiments described herein are not limited to those explicitly introduced and described herein.

Claims

1. A circuit for balancing valley current, comprising an input terminal, a switching transistor, an output terminal, an output sampling unit, an input sampling unit, and a controller, wherein the input terminal is electrically connected to the collector of the switching transistor, the output terminal is electrically connected to the emitter of the switching transistor, the input sampling unit is electrically connected to the input terminal and is used to sample the input voltage, the controller is used to perform valley detection based on the output of the input sampling unit, and the output sampling unit is electrically connected to the output terminal and is used to sample the output voltage, characterized in that... Also comprising: a rising and falling edge determining unit configured to determine a variation trend of the input voltage according to an output of the input sampling unit, wherein the variation trend is rising or falling; a threshold switching unit configured to switch an upper threshold and a lower threshold of the comparator according to the variation trend of the input voltage; the comparator, electrically connected to the output of the output sampling unit, configured to output a comparison signal based on the variation trend of the output voltage, the output voltage, the upper threshold and the lower threshold; the controller further configured to control a state of the switch tube based on the valley bottom detection result and the comparison signal.

2. The circuit for balancing the valley bottom conduction current according to claim 1, wherein, The threshold switching unit switches the upper threshold and the lower threshold of the comparator, comprising: when the variation trend of the input voltage is rising, the upper threshold of the comparator is a rising upper threshold, and the lower threshold of the comparator is a rising lower threshold; when the variation trend of the input voltage is falling, the upper threshold of the comparator is a falling upper threshold, and the lower threshold of the comparator is a falling lower threshold, wherein the rising upper threshold is smaller than the falling upper threshold.

3. The circuit of claim 2, wherein, 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. The circuit of claim 3, wherein, The output sampling unit comprises a first resistor and at least two voltage dividing resistors connected in series between the output and the input of the comparator.

5. A circuit for balancing the valley bottom conduction current as claimed in claim 4, wherein The threshold switching unit comprises at least one threshold switching switch, wherein the at least one voltage dividing resistor is connected in parallel with the threshold switching switch.

6. A circuit for balancing the valley conduction current as claimed in claim 2 or 3, wherein The comparator outputs the comparison signal based on the variation trend of the output voltage, the output voltage, the upper threshold and the lower threshold, comprising: when the variation trend of the input voltage is rising and the variation trend of the output voltage is rising, the output voltage is compared with the rising upper threshold; when the variation trend of the input voltage is rising and the variation trend of the output voltage is falling, the output voltage is compared with the rising lower threshold.

7. A circuit for balancing the valley conduction current as claimed in claim 2 or 3, wherein The comparator outputs the comparison signal based on the variation trend of the output voltage, the output voltage, the upper threshold and the lower threshold, comprising: when the variation trend of the input voltage is falling and the variation trend of the output voltage is rising, the output voltage is compared with the falling upper threshold; when the variation trend of the input voltage is falling and the variation trend of the output voltage is falling, the output voltage is compared with the falling lower threshold.

8. A circuit for balancing the valley conduction current as claimed in any one of claims 1 to 4, wherein The controller controls the state of the switch tube based on the valley bottom detection result and the comparison signal, comprising: when the comparison signal is high and the input voltage is the valley bottom, the switch tube is turned on.

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