CN117134636A - Linear constant current switching power supply - Google Patents

Abstract

A linear constant current switching power supply is provided, including a first capacitor, a second capacitor, and an output capacitor, configured to: when the rectified system input voltage is lower than the system output voltage but higher than the first capacitor and the second capacitor When the voltage on at least one capacitor is, the first capacitor and the second capacitor are connected in parallel with each other, the first capacitor and the second capacitor are respectively charged by the rectified system input voltage via different current paths, and the output capacitor provides a flow through the load. of current.

Description

Linear constant current switching power supply

Technical field

The present invention relates to the field of circuits, and more specifically to a linear constant current switching power supply.

Background technique

Switching power supply, also known as switching power supply and switching converter, is a type of power supply. The function of the switching power supply is to convert a level of voltage into what the user needs through different forms of architecture (for example, fly-back architecture, buck architecture, or boost architecture, etc.) voltage or current.

Contents of the invention

The linear constant current switching power supply according to an embodiment of the present invention includes a first capacitor, a second capacitor, and an output capacitor, and is configured to: when the rectified system input voltage is lower than the system output voltage but higher than the first capacitor and the second When the voltage on at least one of the capacitors is high, the first capacitor and the second capacitor are connected in parallel with each other, the first capacitor and the second capacitor are respectively charged by the rectified system input voltage through different current paths, and the current is provided by the output capacitor. overload current.

Description of the drawings

The present invention can be better understood from the following description of specific embodiments of the invention in conjunction with the accompanying drawings, in which:

Figure 1 shows a schematic diagram of the topology of a traditional linear constant current switching power supply.

FIG. 2 shows the operating waveform diagrams of multiple signals in the linear constant current switching power supply shown in FIG. 1 .

FIG. 3 shows a schematic diagram of the topology of a linear constant current switching power supply according to an embodiment of the present invention.

Figure 4 shows a schematic diagram of the working area division of the linear constant current switching power supply shown in Figure 3 within a power frequency cycle.

FIG. 5 shows an equivalent circuit diagram of the linear constant current switching power supply shown in FIG. 3 when the rectified system input voltage Vin is higher than the system output voltage Vo across the load LED.

Figure 6 shows the equivalent circuit diagram of the linear constant current switching power supply shown in Figure 3 when the rectified system input voltage Vin is slightly lower than the system output voltage Vo across the load LED but higher than the voltage on the capacitors C1 and C2.

Figure 7 shows the equivalent circuit diagram of the linear constant current switching power supply shown in Figure 3 when the rectified system input voltage Vin is significantly lower than the system output voltage Vo across the load LED but higher than the voltage on the capacitors C1 and C2.

Figure 8 shows the equivalent circuit diagram of the linear constant current switching power supply shown in Figure 3 when the rectified system input voltage Vin is lower than the voltage on the capacitors C1 and C2.

FIG. 9A shows the operating waveform diagram of multiple signals when the operating state of the linear constant current switching power supply shown in FIG. 3 includes the operating state of area 2.

FIG. 9B shows the operating waveform diagram of multiple signals when the operating state of the linear constant current switching power supply shown in FIG. 3 does not include the operating state of area 2.

FIG. 10 shows a schematic diagram of the topology of another linear constant current switching power supply according to an embodiment of the present invention.

FIG. 11 shows the operating waveform diagrams of multiple signals of the linear constant current switching power supply shown in FIG. 10 .

Detailed ways

Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The present invention is in no way limited to any specific configurations and algorithms set forth below, but covers any modifications, substitutions and improvements of elements, components and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention. In addition, it should be noted that the term "A and B are connected" used here may mean "A and B are directly connected" or "A and B are indirectly connected via one or more other components."

Figure 1 shows a schematic diagram of the topology of a traditional linear constant current switching power supply. In the linear constant current switching power supply 100 shown in Figure 1, the current flowing through the switch S1 can be sampled through the current sampling resistor Rcs to generate the load current sampling voltage Vcs (since the average current flowing through the output capacitor Co in the steady state is 0 , so the average value of the current flowing through the switch S1 is equal to the current flowing through the load light-emitting diode (LED)), and the switch S1 can be controlled to operate in the saturation region based on the load current sampling voltage Vcs to ensure that the current flowing through the load LED is constant. Since the system input current Iin flows through the switch S1 only when the rectified system input voltage Vin is higher than the system output voltage Vo across the load LED (in this case, the conduction phase angle of the system input current Iin is smaller) , so in order to achieve high power factor (PF), it is necessary to add the bleeder switch S2 and the bleeder resistor Rb. Among them, when the rectified system input voltage Vin is lower than the system output voltage Vo across the load LED (ie, no current flows through When switching S1), the bleeder switch S2 is in a conductive state, so that the system input current Iin forms a bleeder current through the bleeder switch S2 and the bleeder resistor Rb and changes with the change of the rectified system input voltage Vin.

Figure 2 shows the operating waveforms of multiple signals in the linear constant current switching power supply shown in Figure 1, where Vo represents the system output voltage across the load LED, Vin represents the rectified system input voltage, and Vcs represents the load Current sampling voltage, Iin represents the system input current. Combining Figures 1 and 2, it can be seen that when the rectified system input voltage Vin is less than the system output voltage Vo across the load LED, the system input current Iin is discharged through the branch composed of the discharge switch S2 and the discharge resistor Rb. All this energy is lost in the discharge resistor Rb and cannot be transmitted to the load LED, which seriously affects the system efficiency of the linear constant current switching power supply.

In view of the above situation, a linear constant current switching power supply according to embodiments of the present invention is proposed, which can meet certain PF requirements without affecting the system efficiency. For example, it can simultaneously achieve PF>0.9 and system efficiency>82%.

FIG. 3 shows a schematic diagram of the topology of a linear constant current switching power supply according to an embodiment of the present invention. In the linear constant current switching power supply 300 shown in Figure 3, S1, Sa, Sb, Sc, and Sd are semiconductor switching devices. The conduction phase angle of the system input current Iin is increased through parallel charging of capacitors C1 and C2, thereby improving PF ( For example, achieve PF>0.9).

Figure 4 shows a schematic diagram of the working area division of the linear constant current switching power supply shown in Figure 3 within a power frequency cycle. Combining Figures 3 and 4, it can be seen that according to the size of the rectified system input voltage Vin, the working state of the linear constant current switching power supply 300 can be divided into four working areas (i.e., Area 1 to Area 4 shown in Figure 4 ) or three working areas (i.e., Area 1, Area 3, and Area 4 shown in Figure 4, without Area 2).

FIG. 5 shows an equivalent circuit diagram of the linear constant current switching power supply 300 shown in FIG. 3 when the rectified system input voltage Vin is higher than the system output voltage Vo across the load LED. As shown in Figure 5, when the rectified system input voltage Vin is higher than the system output voltage Vo across the load LED, switch S1 works in the saturation zone, switches Sa, Sb, Sc, Sd are in the off state, and the load LED flows through The current is provided by the rectified system input voltage Vin, and the current flowing through the switch S1 is equal to the system input current Iin (the current flow direction is shown by the arrow). At this stage, the linear constant current switching power supply 300 works in area 1. That is to say, when the rectified system input voltage Vin is higher than the system output voltage Vo across the load LED, the capacitors C1 and C2 neither charge nor discharge, and the rectified system input voltage Vin provides the current flowing through the load LED. while charging the output capacitor Co. Here, the system input current Iin flows into the ground through the switch S1 and the current sampling resistor Rcs. The size of the current flowing through the switch S1 can be controlled based on the load current sampling voltage Vcs on the current sampling resistor Rcs to control the size of the current flowing through the load LED. .

FIG. 6 shows an equivalent circuit diagram of the linear constant current switching power supply 300 shown in FIG. 3 when the rectified system input voltage Vin is slightly lower than the system output voltage Vo across the load LED but higher than the voltages on the capacitors C1 and C2 . As shown in Figure 6, when the rectified system input voltage Vin is slightly lower than the system output voltage Vo on the load LED but higher than the voltage on each of the capacitors C1 and C2, the switches S1, Sa, Sb, Sc , Sd are all in the off state, the system input current Iin is 0, and the current flowing through the load LED is provided by the output capacitor Co (the current flow direction is as shown by the arrow). At this stage, the linear constant current switching power supply 300 works in area 2. That is, when the rectified system input voltage Vin is slightly lower than the system output voltage Vo across the load LED but higher than the voltage across each of the capacitors C1 and C2 (e.g., the rectified system input voltage Vin is the same as the capacitor When the difference between the voltages on at least one of the capacitors C1 and C2 is greater than a predetermined threshold), the capacitors C1 and C2 neither charge nor discharge, and the output capacitor Co provides a current flowing through the load LED.

It should be noted that if the linear constant current switching power supply 300 has higher requirements for system efficiency, the working state of the linear constant current switching power supply 300 can be divided into four working areas as shown in Figure 4; if the linear constant current switching power supply 300 If the requirements for PF or total harmonic distortion (THD) are high, the working state of the linear constant current switching power supply 300 can be divided into three working areas other than area 2 shown in Figure 4 (i.e., area 1, area 3, and area 4).

FIG. 7 shows an equivalent circuit diagram of the linear constant current switching power supply 300 shown in FIG. 3 when the rectified system input voltage Vin is significantly lower than the system output voltage Vo across the load LED but higher than the voltages on the capacitors C1 and C2 . As shown in Figure 7, when the rectified system input voltage Vin is significantly lower than the system output voltage Vo across the load LED but is still higher than the voltage on at least one of the capacitors C1 and C2, the switches S1 and Sc are off state, the switches Sa and Sb work in the saturation zone, the switch Sd is in the on state, the rectified system input voltage Vin charges the capacitor C1 through the switch Sa and charges the capacitor C2 through the switches Sb and Sd, and the current flowing through the load LED is The output capacitor Co provides the current flow direction as shown by the arrow. At this stage, the linear constant current switching power supply 300 operates in area 3. That is, when the rectified system input voltage Vin is significantly lower than the system output voltage Vo across the load LED but is still higher than the voltage on at least one of the capacitors C1 and C2 (for example, the rectified system input voltage Vin is When the difference between the voltages on at least one of the capacitors C1 and C2 is less than a predetermined threshold), the capacitors C1 and C2 are connected in parallel with each other, and the capacitors C1 and C2 are respectively charged by the rectified system input voltage Vin through different current paths. , and the current flowing through the load LED is provided by the output capacitor Co. Specifically, the rectified system input voltage Vin charges the capacitor C1 through the switch Sa. The resistor Rc1 detects the charging current of the capacitor C1 and converts it into a voltage. The current flowing through the switch Sa can be controlled based on the voltage on the resistor Rc1. The size thereby controls the size of the charging current of capacitor C1. At the same time, the rectified system input voltage Vin charges the capacitor C2 through the switches Sb and Sd. The resistor Rc2 detects the charging current of the capacitor C2 and converts it into a voltage. The voltage flowing through the switch Sb can be controlled based on the voltage on the resistor Rc2. The size of the current thereby controls the size of the charging current of capacitor C2.

FIG. 8 shows an equivalent circuit diagram of the linear constant current switching power supply 300 shown in FIG. 3 when the rectified system input voltage Vin is lower than the voltages on the capacitors C1 and C2. As shown in Figure 8, when the rectified system input voltage Vin is lower than the voltage on each capacitor C1 and C2, the switches Sb and Sc are in the on state, the switch S1 works in the saturation zone, and the rectified system The input voltage Vin can neither provide current to the load LED nor charge the capacitors C1 and C2. The system input current Iin can only be zero. The capacitors C1 and C2 are discharged in series through the switches Sb and Sc to provide current to the load LED (the current flows as indicated by the arrows). shown), at this stage the linear constant current switching power supply 300 works in area 4. That is, when the rectified system input voltage Vin is lower than the voltage across each of the capacitors C1 and C2, the capacitors C1 and C2 are in series with each other and the current flowing through the load LED is provided by the discharge of the capacitors C1 and C2. At the same time, the current sampling resistor Rcs detects the size of the current flowing through the load LED (ie, the discharge current of the capacitors C1 and C2) and converts it into a load current sampling voltage, which can be controlled based on the load current sampling voltage on the current sampling resistor Rcs. The magnitude of the current flowing through the switch S1 thereby controls the magnitude of the discharge current of the capacitors C1 and C2 (ie, the magnitude of the current flowing through the load LED).

In the linear constant current switching power supply 300 shown in FIG. 3 , the switches Sc and Sd control the series and parallel connection of the capacitors C1 and C2 with each other. When the switch Sd is in the on state and the switch Sc is in the off state, the capacitors C1 and C2 are connected in parallel with each other. When the switch Sd is in the off state and the switch Sc is in the on state, the capacitors C1 and C2 are connected in series with each other.

9A shows the working waveform diagram of multiple signals when the working state of the linear constant current switching power supply 300 shown in FIG. 3 includes the working state of area 2, where Vo represents the system output voltage Vo across the load LED and Vin represents The rectified system input voltage, Vcs represents the load current sampling voltage, and Iin represents the system input current. As shown in Figure 9A, time t0 to time t1 correspond to the working state of area 1. At this time, the rectified system input voltage Vin provides current to the load LED and charges the output capacitor Co; time t1 to time t2 corresponds to the working state of area 2. , at this time, the output capacitor Co provides current to the load LED; t2 time-t3 time corresponds to the working state of area 3. At this time, the output capacitor Co still provides current to the load LED, and at the same time, the rectified system input voltage Vin charges the capacitors C1 and C2 ; Time t3 to time t4 correspond to the working state of area 4, and capacitors C1 and C2 are connected in series to discharge to the load LED. It should be noted that the working status is the same at the symmetrical points on both sides of the power frequency cycle.

9B shows the operating waveform diagram of multiple signals when the operating state of the linear constant current switching power supply 300 shown in FIG. 3 does not include the operating state of area 2, where Vo represents the system output voltage Vo, Vin at both ends of the load LED. Represents the rectified system input voltage, Vcs represents the load current sampling voltage, and Iin represents the system input current. As shown in Figure 9B, time t5-t6 corresponds to the working state of area 1. At this time, the rectified system input voltage Vin provides current to the load LED and charges the output capacitor Co; time t6-t7 corresponds to the working state of area 3. , at this time, the output capacitor Co provides current to the load LED, and at the same time, the rectified system input voltage Vin charges the capacitors C1 and C2; t7 time-t8 time corresponds to the working state of area 4, at this time, the capacitors C1 and C2 are discharged in series to the load LED . It should be noted that the working status is the same at the symmetrical points on both sides of the power frequency cycle.

FIG. 10 shows a schematic diagram of the topology of another linear constant current switching power supply 1000 according to an embodiment of the present invention. In order to achieve a THD of less than 20%, the operating state of the linear constant current switching power supply 1000 shown in Figure 10 does not include the operating state of area 2, and during the operating state of area 4 (that is, during the series discharge of capacitors C1 and C2), The system input current Iin forms a leakage current through the switch Se and the resistor Rb and changes with the change of the rectified system input voltage Vin. That is to say, when the current flowing through the load LED is provided by the discharge of capacitors C1 and C2, the resistor Rb is used as a bleed resistor, the switch Se is used as a bleed switch, and the system input current Iin forms a bleed current through the resistor Rb and the switch Se. And changes with the change of the rectified system input voltage Vin. Other details of the linear constant current switching power supply 1000 shown in FIG. 10 are the same as the linear constant current switching power supply 300 described in conjunction with FIGS. 3 to 9B , and therefore will not be described again.

Figure 11 shows the operating waveform diagram of multiple signals of the linear constant current switching power supply 1000 shown in Figure 10, where Vo represents the system output voltage at both ends of the load LED, Vin represents the rectified system input voltage, and Vcs represents the load current. Sampling voltage, Iin represents the system input current. As shown in Figure 11, time t0 to time t1 correspond to the working state of area 1. At this time, the rectified system input voltage Vin provides current to the load LED and charges the output capacitor Co; time t1 to time t2 corresponds to the working state of area 3. , at this time, the output capacitor Co provides current to the load LED, and at the same time, the rectified system input voltage Vin charges the capacitors C1 and C2; t2 time-t3 time corresponds to the working state of area 4, at this time, the capacitors C1 and C2 are discharged in series to the load LED , the system input current Iin forms a discharge current through the switch Se and the resistor Rb and changes with the change of the rectified system input voltage Vin. It should be noted that the working status is the same at the symmetrical points on both sides of the power frequency cycle.

The present invention increases the conduction phase angle of the system input current Iin by charging the capacitors C1 and C2 in parallel, and improves the PF of the linear constant current switching power supply. Then, when the rectified system input voltage Vin is so low that it cannot provide current to the load LED. When the capacitors C1 and C2 cannot be charged, the load LED is discharged through the capacitors C1 and C2 in series, and the previously charged energy is discharged to the load LED, which improves the system efficiency while achieving high PF, that is, achieving high PF and high Linear constant current switching power supply for system efficiency.

The present invention may be implemented in other specific forms without departing from its spirit and essential characteristics. For example, algorithms described in specific embodiments may be modified without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative rather than restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and everything within the meaning and equivalents of the claims is All changes within the scope are therefore included in the scope of the invention.

Claims (9)

1. A linear constant current switching power supply, including a first capacitor, a second capacitor, and an output capacitor, configured as: The first capacitor and the second capacitor are connected in parallel with each other when the rectified system input voltage is lower than the system output voltage but higher than the voltage on at least one of the first capacitor and the second capacitor, The first capacitor and the second capacitor are respectively charged by the rectified system input voltage via different current paths, and the current flowing through the load is provided by the output capacitor. 2. The linear constant current switching power supply according to claim 1, further configured to: When the rectified system input voltage is lower than the voltage on each of the first capacitor and the second capacitor, the first capacitor and the second capacitor are connected in series with each other. Discharging a capacitor and the second capacitor provides current flow through the load. 3. The linear constant current switching power supply according to claim 1, further configured to: When the rectified system input voltage is higher than the system output voltage, the first capacitor and the second capacitor neither charge nor discharge, and the rectified system input voltage provides a flow through the The load current simultaneously charges the output capacitor. 4. The linear constant current switching power supply according to claim 1, further configured to: When the difference between the rectified system input voltage and the voltage on at least one of the first capacitor and the second capacitor is less than a predetermined threshold, the first capacitor and the second capacitor In parallel with each other, the first capacitor and the second capacitor are respectively charged by the rectified system input voltage via different current paths, and the current flowing through the load is provided by the output capacitor. 5. The linear constant current switching power supply according to claim 4, further configured to: When the difference between the rectified system input voltage and the voltage on at least one of the first capacitor and the second capacitor is greater than the predetermined threshold, the first capacitor and the second capacitor are The two capacitors neither charge nor discharge, and the output capacitor provides the current flowing through the load. 6. The linear constant current switching power supply of claim 2, further comprising a bleeder resistor and a bleeder switch, wherein when the first capacitor and the second capacitor are discharging to provide a current flowing through the load , the system input current forms a bleeding current via the bleeding resistor and the bleeding switch and changes with the change of the rectified system input voltage. 7. The linear constant current switching power supply according to claim 1, further configured to: The first capacitor is charged by the rectified system input voltage via a first switch, and the charging current of the first capacitor is detected by a first resistor, wherein the flow is controlled based on the voltage across the first resistor. The size of the current flowing through the first switch. 8. The linear constant current switching power supply according to claim 1, further configured to: The second capacitor is charged by the rectified system input voltage via a second switch, and the charging current of the second capacitor is detected by a second resistor, wherein the flow is controlled based on the voltage across the second resistor. The size of the current flowing through the second switch. 9. The linear constant current switching power supply according to claim 8, further configured to: The third switch and the fourth switch control the series connection and parallel connection between the first capacitor and the second capacitor, where: When the third switch is in the on state and the fourth switch is in the off state, The first capacitor and the second capacitor are connected in parallel with each other, When the third switch is in the off state and the fourth switch is in the on state, The first capacitor and the second capacitor are connected in series with each other.