CN116430093A

CN116430093A - Circuit for measuring power supply voltage of power supply end of LED control chip

Info

Publication number: CN116430093A
Application number: CN202211718523.0A
Authority: CN
Inventors: 李可; 李萌; 李卓研
Original assignee: On Bright Electronics Shanghai Co Ltd
Current assignee: On Bright Electronics Shanghai Co Ltd
Priority date: 2022-12-29
Filing date: 2022-12-29
Publication date: 2023-07-14
Also published as: TWI847604B; TW202428070A

Abstract

The invention provides a circuit for measuring the supply voltage of a power supply end of an LED control chip. The power supply terminal supplies power to the energy storage device connected to the power supply pin of the LED control chip via the high-voltage pin of the LED control chip, so that the energy storage device supplies working current to the LED control chip via the power supply pin, and the circuit comprises: the first control unit is connected between the high-voltage pin and the power pin and is used for switching on or switching off the connection between the high-voltage pin and the power pin according to a first control signal; a voltage measurement unit connected between the high voltage pin and the reference ground for starting or stopping measurement of the power supply voltage via the high voltage pin according to the second control signal, the voltage measurement unit stopping measurement of the power supply voltage in a case that the first control unit turns on the connection between the high voltage pin and the power supply pin; the voltage measurement unit starts measurement of the supply voltage in case the first control unit disconnects the high voltage pin from the supply pin.

Description

Circuit for measuring power supply voltage of power supply end of LED control chip

Technical Field

The invention relates to the field of circuits, in particular to a circuit for measuring a power supply voltage of a power supply end of an LED control chip.

Background

LED lighting has become an integral part of people's daily lives, and LED driving circuits for powering LEDs are increasingly used.

LED drive circuits typically convert an external supply current to a constant current under the control of an LED control chip to power the LEDs. The LED control chip needs to supply power to the energy storage device connected to the power supply pin of the LED control chip using the power supply voltage of the power supply terminal, so that the energy storage device can provide working current for the LED control chip. In order to achieve relevant control of the LED control chip, such as overvoltage protection, the supply voltage of the supply terminal needs to be measured. However, the measurement of the supply voltage is generally affected by the working state of the LED driving chip, which results in inaccurate measurement results, thereby affecting the related control operation of the LED control chip and even causing potential safety hazards to the LED control chip.

Therefore, a way to more accurately measure the supply voltage of the supply terminal is needed.

Disclosure of Invention

According to an exemplary embodiment of the present invention, there is provided a circuit for measuring a supply voltage of a supply terminal of an LED control chip, the supply terminal for supplying power to an energy storage device connected to a power supply pin of the LED control chip via a high voltage pin of the LED control chip such that the energy storage device supplies an operating current to the LED control chip via the power supply pin, wherein the circuit includes: a first control unit configured to be connected between the high voltage pin and the power supply pin for switching on or off connection between the high voltage pin and the power supply pin according to a first control signal; and a voltage measurement unit configured to be connected between the high voltage pin and a reference ground for turning on or off measurement of the power supply voltage via the high voltage pin according to a second control signal, wherein the voltage measurement unit stops measurement of the power supply voltage via the high voltage pin in a case where the first control unit turns on connection between the high voltage pin and the power supply pin; the voltage measurement unit turns on measurement of the supply voltage via the high voltage pin if the first control unit disconnects the high voltage pin from the power supply pin.

According to the circuit for measuring the power supply voltage of the power supply terminal of the LED control chip, according to the exemplary embodiment of the invention, the influence of the working state of the LED control chip on the measurement of the power supply voltage can be prevented by stopping the measurement of the power supply voltage of the power supply terminal during the period when the high-voltage pin of the LED control chip is connected to the power supply pin so that the power supply terminal supplies power to the energy storage device connected to the power supply pin, and measuring the power supply voltage of the power supply terminal during the period when the high-voltage pin of the LED control chip is disconnected from the power supply pin so that the power supply terminal does not supply power to the energy storage device connected to the power supply pin, so that the accuracy of measuring the power supply voltage can be improved.

Drawings

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

fig. 1 shows a schematic circuit diagram of an LED driving circuit with an LED driving chip according to an exemplary embodiment.

Fig. 2 shows a waveform diagram of voltage signals and current signals in the circuit of fig. 1 according to an exemplary embodiment.

Fig. 3 shows a schematic block diagram of a circuit for measuring a supply voltage of a supply terminal of an LED control chip according to an exemplary embodiment of the invention.

Fig. 4 shows a schematic circuit diagram of a circuit for measuring a supply voltage of a supply terminal of an LED control chip according to an exemplary embodiment of the invention.

Fig. 5 shows waveforms of voltage signals and current signals in the circuit of fig. 4 according to an exemplary embodiment of the present invention.

Detailed Description

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. It will be apparent, however, 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 showing examples of the invention. The present invention is in no way limited to any particular configuration and algorithm set forth below, but rather covers any modification, substitution, and improvement 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 have not been shown in order to avoid unnecessarily obscuring the present invention.

Fig. 1 shows a schematic circuit diagram of an LED driving circuit 1000 with an LED driving chip 100 according to an exemplary embodiment.

As shown in fig. 1, the LED driving circuit 1000 is connected to the external power supply line Vbus via an input terminal Nin1 and to the LEDs via a first output terminal Nout1 and a second output terminal Nout2 to supply power to the LEDs using the power of the external power supply line Vbus. The power supplied by the power supply line Vbus may be rectified mains or the like.

The LED driving circuit 1000 has an LED control chip 100, and can convert the current of the external power supply line Vbus into a constant current for supplying power to the LEDs using the LED control chip 100. For example, the constant current control module 120 of the LED driving chip 100 may be connected to the GATE G of the constant current switch M2 via the GATE pin GATE and serve to provide a control signal to the GATE G of the constant current switch M2 to generate a constant current for supplying power to the LED by controlling the on or off of the constant current switch M2.

In order for the LED control chip 100 to obtain the power required for operation, the high voltage pin HV of the LED control chip 100 may be connected to the power supply line Vbus to supply power to the energy storage device (e.g., the capacitor Cvdd) connected to the power supply pin VDD of the LED control chip 100 through the power supply line Vbus, so that the energy storage device Cvdd supplies the operating current to the LED control chip 100 via the power supply pin VDD. For example, as shown in fig. 1, in the LED control chip 100, the high voltage pin HV may be connected to a power pin VDD through a switch M1, and the power pin VDD is connected to a capacitor Cvdd as an energy storage device.

In order to provide electrostatic discharge (ESD) protection to the LED control chip 100 and to prevent reverse current flow from the LED control chip 100 to the power supply line Vbus, a resistor Rp may be provided between the power supply line Vbus and the high voltage pin HV. For example, the resistor Rp may have a resistance value of 1-20K ohms when the supply voltage of the supply line Vbus is high, e.g., the average voltage is greater than 300V. At this time, the switch M1 may be a high voltage device, for example, a high voltage device having an operating voltage greater than 500V.

Since related control such as overvoltage protection is required for the LED chip, measurement of the supply voltage of the supply line Vbus is required. For example, as shown in fig. 1, the divided voltage of the voltage at the high voltage pin HV may be measured via the measurement terminal Vc by dividing the voltage at the high voltage pin HV by resistors R2 and R3 connected in series between the high voltage pin HV and the reference ground, thereby measuring the supply voltage of the supply line Vbus.

However, when the switch M1 is turned on, the power supply line Vbus supplies power to the capacitor Cvdd, and the current Ihv flowing through the resistor Rp is the operating current of the LED control chip 100, so that there is a corresponding voltage drop across the resistor Rp. In addition, the operating current of the LED control chip 100 may vary due to different operations or different operating states of the LED control chip. For example, the operation currents of the LED control chip 100 are different from each other at the moment when the LED control chip 100 controls the switch M2 to be turned on, during the time when the control switch M2 is turned on, at the moment when the control switch M2 is turned off, and during the time when the control switch M2 is turned off. In addition, when the LED control chip 100 is in the start-up state, the normal operation state, the protection state, and the fast response state, the operation currents of the LED control chip 100 are also different from each other. The constantly changing operating current of the LED control chip 100 may cause the voltage drop across the resistor Rp to constantly change, which may lead to inaccurate supply voltage measured via the measurement terminal Vc, which may lead to misjudgment of the LED control chip and thus cause misoperations, and even cause potential safety hazards to the LED control chip.

As shown in fig. 2, the power supply line Vbus has a power supply voltage V1, and before time t1 (left side of time t1 of fig. 2), the switch M1 is in an off state, and the power supply line Vbus does not supply power to the capacitor Cvdd. The sum of the resistance of resistor R2 and the resistance of resistor R3 in fig. 1 may be set much larger than the resistance of resistor Rp, so that before time t1, the current Ihv flowing through resistor Rp may be approximately 0, the voltage drop across resistor Rp may be negligible, and the voltage at high voltage pin HV may be approximately the supply voltage V1 of supply line Vbus. At this time, the partial pressure Vc1 measured at the measurement terminal Vc may be vc1=v1×r2/(r2+r3), and it should be understood that R2 and R3 in this equation represent the resistance values of the resistors R2 and R3, respectively.

At and after time t1 (right side of time t1 of fig. 2), switch M1 is in an on state, power supply line Vbus supplies power to capacitor Cvdd, and at this time, current Ihv flowing through resistor Rp is operating current I1 of LED control chip 100. Accordingly, the voltage drop across resistor Rp causes the voltage at high voltage pin HV to drop from supply voltage V1 to voltage V2. The partial pressure measured at the measurement terminal Vc is changed from Vc1 to v2= (V1-i1×rp) ×r2/(r2+r3). Therefore, when the operating current I1 of the LED control chip 100 is continuously changed during the power supply of the power supply line Vbus to the capacitor Cvdd, the power supply voltage measured via the measurement terminal Vc is changed accordingly and is very inaccurate.

To at least partially overcome the above-described drawbacks, a circuit for measuring a supply voltage of a supply terminal of an LED control chip is provided according to an exemplary embodiment of the present application.

Fig. 3 shows a schematic block diagram of a circuit 210 for measuring the supply voltage of the supply terminal of the LED control chip 200 according to an exemplary embodiment of the invention.

The power supply terminal Vin as shown in fig. 3 is used to supply power to the energy storage device connected to the power supply pin VDD of the LED control chip 200 via the high voltage pin HV of the LED control chip 200, so that the energy storage device supplies an operating current to the LED control chip 200 via the power supply pin VDD.

In one embodiment, the energy storage device may be a first capacitor C1 (e.g., capacitor Cvdd shown in fig. 1), the first capacitor C1 being connected between the power supply pin VDD and the reference ground.

In one embodiment, the LED control chip 200 may be used in an LED driving circuit for converting the current of an external power supply line into a constant current to power the LEDs. For example, the LED driving circuit may be the driving circuit shown in fig. 1, and the external power supply line may be the power supply line Vbus shown in fig. 1.

In one embodiment, the power supply terminal Vin may be a terminal (e.g., an input terminal Nin1 shown in fig. 1) of the external power supply line Vbus for connection to the LED control chip 200, or the power supply terminal Vin may be a predetermined terminal of the LED driving circuit capable of providing a power supply voltage to the LED control chip 200. The average voltage value of the supply voltage may be greater than the second voltage value.

For example, in the case where the power supply terminal Vin is the input terminal Nin1 of the external power supply line Vbus, the power supply voltage may be rectified mains, and the average voltage value of the power supply voltage may be greater than 300V.

In the case where the power supply terminal Vin is a predetermined terminal of the LED driving circuit capable of supplying a power supply voltage to the LED control chip 200, the predetermined terminal may be a drain D of a constant current switch (e.g., a switch M2 shown in fig. 1) of the LED driving circuit 200 in one embodiment. Similarly to that shown in fig. 1, the gate G of the constant current switch M2 may be connected to the constant current control module 120 of the LED control chip 200, the drain D of the constant current switch M2 may be connected to the first output terminal Nout1 of the LED driving circuit via the diode D1, and to the second output terminal Nout2 of the LED driving circuit via the inductor L1, and the source S of the constant current switch M2 may be connected to the ground. The external power supply line Vbus may be connected to a first output terminal Nout1, and the first output terminal Nout1 and a second output terminal Nout2 may be used to connect LEDs. In this case, for example, the average voltage value of the supply voltage may be greater than 500V.

In other words, the circuit 210 shown in fig. 3 may be used in place of the circuit 110 shown in fig. 1, and other parts of the LED control chip 200 shown in fig. 3 may be identical to those of the LED control chip 100 shown in fig. 1. Alternatively, the circuit 210 shown in fig. 3 may be applied to a modified circuit of the LED driving circuit shown in fig. 1, for example, the power supply terminal Vin of the circuit 210 shown in fig. 3 may not be connected to the external power supply line Vbus shown in fig. 1, but connected to the drain D of the switch M2 shown in fig. 1 as described above to supply the first capacitor C1 (Cvdd) with the voltage at the drain of the switch M2 in case that the switch M2 is turned off, and to use the circuit 210 according to an exemplary embodiment of the present invention in case that the switch M2 is turned off. It should be understood that the LED control chip shown in fig. 1 and 3 may further include other modules not shown.

Referring to fig. 3, a circuit 210 for measuring a supply voltage of a supply terminal of an LED control chip 200 according to an exemplary embodiment of the present invention may include: a first control unit 211 and a voltage measurement unit 212.

The first control unit 211 may be configured to be connected between the high voltage pin HV and the power supply pin VDD for switching on or off the connection between the high voltage pin HV and the power supply pin VDD according to a first control signal (e.g., signal a shown in fig. 4).

The voltage measurement unit 212 may be configured to be connected between the high voltage pin HV and a reference ground for turning on or off the measurement of the supply voltage via the high voltage pin HV according to a second control signal (e.g., signal B shown in fig. 4).

In one embodiment, in case the first control unit 211 turns on the connection between the high voltage pin HV and the power supply pin VDD, the voltage measurement unit 212 stops the measurement of the power supply voltage via the high voltage pin HV; in case the first control unit 211 disconnects the high voltage pin HV from the power supply pin VDD, the voltage measurement unit 212 turns on the measurement of the power supply voltage via the high voltage pin HV.

An exemplary embodiment of circuit 210 is described in detail below with reference to fig. 4.

Fig. 4 shows a schematic circuit diagram of a circuit 210 for measuring the supply voltage of the supply terminal of the LED control chip 200 according to an exemplary embodiment of the invention.

In the above embodiments, the LED driving circuit for which the LED control chip is used may have a power factor greater than a predetermined value (e.g., greater than 0.9 or other values). The supply voltage may be a time-varying voltage, for example, a voltage having a waveform similar to a sine wave (e.g., rectified mains).

In this case, as shown in fig. 4, the circuit 210 may further include: the current limiting unit 213 may be configured to be connected between the power supply terminal Vin and the high voltage pin HV, to provide electrostatic discharge (ESD) protection to the LED control chip 200 by limiting a magnitude of current between the power supply terminal Vin and the high voltage pin HV, and to limit a backflow of current from the LED control chip 200 to the power supply terminal Vin during a variation of a power supply voltage (e.g., when the power supply voltage is 0). In one embodiment, the current limiting unit 213 may be a first resistor R1 having a first resistance value, for example, a resistor Rp in fig. 1.

As shown in fig. 4, in one embodiment, the voltage measurement unit 212 may include: a voltage dividing unit and a measuring unit.

The voltage dividing unit may be configured to be connected between the high voltage pin HV and a reference ground for dividing a voltage at the high voltage pin HV. The measuring unit may be configured to be connected to the voltage dividing unit for switching on or off the measurement of the supply voltage via the division of the voltage at the measurement high voltage pin HV in accordance with the second control signal B.

In one embodiment, the voltage dividing unit may include: a first voltage dividing unit R2 and a second voltage dividing unit R3.

The first voltage dividing unit R2 may be configured to be connected between the high voltage pin HV and the first node N1. In one embodiment, the first voltage dividing unit may be a second resistor R2 having a second resistance value, and the second resistor R2 may be the same as the resistor R2 in fig. 1.

The second voltage dividing unit R3 may be configured to be connected between the first node N1 and the reference ground, the voltage at the first node N1 being a divided voltage of the voltage at the high voltage pin HV. In one embodiment, the second voltage dividing unit R3 may be a third resistor R3 having a third resistance value, and the third resistor R3 may be the same as the resistor R3 in fig. 1. In one embodiment, the sum of the above second resistance and third resistance may be at least a second order of magnitude greater than the first resistance, i.e., (r2+r3) > > R1, where R1, R2, and R3 in the inequality represent the first resistance, the second resistance, and the third resistance, respectively.

In case the operating current is a time-varying current, the current limiting unit 213 (resistor R1 (Rp)) may have (flow) the operating current and the measuring unit may stop the measurement of the supply voltage when the first control unit 211 switches on the connection between the high voltage pin HV and the supply pin VDD. When the first control unit 211 disconnects the high voltage pin HV from the power supply pin VDD, the current limiting unit 213 may have (flow) a current at least a first order of magnitude smaller than the operating current (i.e. a current substantially smaller than the operating current of approximately 0), and the measurement unit may turn on the measurement of the supply voltage.

With the above arrangement, the measurement of the power supply voltage can be started only when the power supply terminal Vin does not supply power to the first capacitor C1, that is, when the current flowing through the resistor R1 is small, and thus the voltage drop of the resistor R1 can be ignored, so that the measurement is not affected by the change of the operating current of the LED control chip, and the measurement is more accurate.

In one embodiment, the measurement unit may include: a first switch s1 and a memory cell C2.

The first switch s1 may be configured to be connected between the first node N1 and the measurement terminal Vc for being turned on or off according to the second control signal B to measure the divided voltage of the voltage at HV via the measurement terminal Vc with the first switch s1 turned on. Since (r2+r3) > > R1, this partial pressure can be regarded as corresponding to the supply voltage.

The storage unit C2 may be configured to be connected between the measurement terminal Vc and the reference ground for storing the partial pressure measured via the measurement terminal Vc in case the first switch s1 is turned on and for maintaining the measured partial pressure at the measurement terminal in case the first switch s1 is turned off. In one embodiment, the memory cell C2 may be a second capacitor C2.

Thereby, the supply voltage can be read/detected at the supply terminal Vc also when the measurement unit stops measuring the supply voltage. Thereby facilitating the ready reading of the power supply voltage and the related control of the LED chip.

As shown in fig. 4, in one embodiment, the first control unit 211 may be a second switch s2, and the second switch s2 may be turned on or off according to the first control signal a.

In addition, to enhance the ease of placement of the circuit 210, the circuit 210 may also retain the corresponding elements shown in fig. 1, for example, in one embodiment, the circuit 210 may further include: the second control unit 214, the second control unit 214 may be configured to be connected between the high voltage pin HV and the first control unit 211 for turning on or off the power supply of the power supply terminal Vin to the energy storage device C1 (Cvdd) via the high voltage pin HV according to a power supply signal (not shown). For example, the second control unit 214 may be the switch M1 shown in fig. 1.

For example, in the case where the power supply terminal Vin is a corresponding terminal Nin of the external power supply line Vbus, the power supply signal may turn on the power supply from the power supply terminal Vin to the energy storage device C1 according to the start signal of the LED control chip, and stop the power supply from the power supply terminal Vin to the energy storage device C1 according to the off signal of the LED control chip. In the case where the power supply terminal Vin is the drain D of the constant current switch M1, the power supply signal may turn on the power supply from the power supply terminal Vin to the energy storage device C1 according to the off signal of the switch M1, and stop the power supply from the power supply terminal Vin to the energy storage device C1 according to the on signal of the switch M1.

Accordingly, the first control unit 211 may be configured to be connected between the second control unit 214 and the power supply pin VDD for switching on or off the connection between the high voltage pin HV and the power supply pin VDD according to the first control signal a in case that the second control unit 214 turns on the power supply of the power supply terminal Vin to the energy storage device C1 via the high voltage pin HV.

In the above manner, the circuit 210 according to the exemplary embodiment of the present invention can be conveniently provided without changing the overall layout of the circuit 110 shown in fig. 1.

Furthermore, in order to generate the above first control signal a and second control signal B, in one embodiment, the circuit 210 according to an exemplary embodiment of the present invention may further include: the signal generating unit 215, the signal generating unit 215 may be configured to generate the first control signal a and the second control signal B as pulse width modulation signals.

In order to enable the first capacitor C1 to normally supply the LED control chip 200 with the corresponding operating power during the power supply to the first capacitor C1 by the first control signal a turning off the power supply terminal Vin, the voltage across the first capacitor C1 needs to be maintained at a substantially stable voltage, i.e., the voltage of the first capacitor C1 should not vary too much. Thus, in one embodiment, the first control signal a may have a predetermined duty cycle that may be such that the amount of change in the voltage across the first capacitor C1 during the period when the second switch s2 is turned off according to the first control signal a is less than a first predetermined value, for example less than a predetermined percentage. For example, the duty cycle may be set by the equation Δu×c=i×t, where Δu may represent a voltage change, C may represent a capacitance value of the first capacitor C1, I may represent a current provided by the first capacitor C1, and t may represent time, e.g., a time when the second switch S2 is turned off.

In one embodiment, the first switch s1 and the second switch s2 may be switches having the same on level (for example, both are NMOS transistors or both are PMOS transistors), and the first control signal a and the second control signal B may be inverted signals.

It should be understood that the first switch s1 and the second switch s2 may also be switches with different on levels (e.g. one NMOS transistor and one PMOS transistor), in which case the first control signal a and the second control signal B may be the same signal.

Fig. 5 is an example in which the first switch s1 and the second switch s2 are NMOS transistors, and the first control signal a and the second control signal B are inverted signals.

As shown in fig. 5, before time T1 (to the left of time T1 of fig. 5), switch M1 is in an off state, power supply terminal Vin is not supplying power to first capacitor C1, current Ihv flowing through resistor Rp may be approximately 0, and the voltage at high voltage pin HV may be approximately the power supply voltage V1 of power supply terminal Vin. The first control signal a may have a low level (may also have a high level), the second control signal B may have a high level, the first switch s1 is turned on, the second switch s2 is turned off (may also be turned on), and at this time, the partial voltage Vc1 measured at the measurement terminal Vc may be vc1=v1×r2/(r2+r3), which is the same as fig. 2.

At and after time T1, switch M1 is in the on state.

During the time T1 to the time T2, the first control signal a may have a high level, the second control signal B may have a low level, the first switch s1 may be turned off, the second switch s2 may be turned on, and the current Ihv flowing through the first resistor R1 (Rp) is the operating current I1 of the LED control chip. Accordingly, the voltage drop across resistor Rp causes the voltage at high voltage pin HV to drop from supply voltage V1 to voltage V2. At this time, the previously measured divided voltage Vc1 is held at the measurement terminal Vc due to the second capacitor C2.

During the time T2 to time T3, the first control signal a may have a low level, the second control signal B may have a high level, the first switch s1 may be turned on, the second switch s2 may be turned off, the power supply terminal Vin does not supply power to the first capacitor C1, the current Ihv flowing through the resistor Rp may be approximately 0, and the voltage at the high voltage pin HV may be approximately the power supply voltage V1 of the power supply terminal Vin. At this time, the partial pressure Vc1 measured at the measurement terminal Vc may be vc1=v1×r2/(r2+r3).

Therefore, the partial pressure Vc1 measured at the measurement terminal Vc can be ensured to accurately correspond to the power supply voltage, and the accuracy of measuring the power supply voltage is improved.

It should be understood that fig. 5 (and fig. 2) is only a schematic waveform diagram, and that fig. 5 shows only a short period of time in the case where the power supply voltage is a voltage that varies with time (e.g., has a waveform similar to a sine wave), and thus the power supply voltage is approximately shown as a constant voltage, but the power supply voltage may have any waveform different from that shown in fig. 5.

It should be understood that the various values shown above are merely examples, and that these values may be set to any of various values as desired.

The functional blocks shown in the above-described structural block diagrams may be implemented in hardware, software, firmware, or a combination thereof. When implemented in hardware, it may be, for example, an electronic circuit, an Application Specific Integrated Circuit (ASIC), suitable firmware, a plug-in, a function card, or the like. When implemented in software, the elements of the invention are the programs or code segments used to perform the required tasks. The program or code segments may be stored in a machine readable medium or transmitted over transmission media or communication links by a data signal carried in a carrier wave. A "machine-readable medium" may include any medium that can store or transfer information. Examples of machine-readable media include electronic circuitry, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio Frequency (RF) links, and the like. The code segments may be downloaded via computer networks such as the internet, intranets, etc.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. For example, the algorithms described in particular 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 and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims

1. A circuit for a LED control chip for measuring a supply voltage of a supply terminal for supplying power to an energy storage device connected to a power supply pin of the LED control chip via a high voltage pin of the LED control chip such that the energy storage device provides an operating current to the LED control chip via the power supply pin, wherein the circuit comprises:

a first control unit configured to be connected between the high voltage pin and the power supply pin for switching on or off connection between the high voltage pin and the power supply pin according to a first control signal; and

a voltage measurement unit configured to be connected between the high voltage pin and a reference ground for turning on or off measurement of the supply voltage via the high voltage pin according to a second control signal,

wherein the voltage measurement unit stops measurement of the power supply voltage via the high voltage pin in a case where the first control unit turns on the connection between the high voltage pin and the power supply pin; the voltage measurement unit turns on measurement of the supply voltage via the high voltage pin if the first control unit disconnects the high voltage pin from the power supply pin.

2. The circuit of claim 1, wherein the supply voltage is a time-varying voltage,

wherein the circuit further comprises:

and the current limiting unit is configured to be connected between the power supply end and the high-voltage pin, and is used for providing electrostatic discharge protection for the LED control chip by limiting the current between the power supply end and the high-voltage pin and limiting the current backflow from the LED control chip to the power supply end in the process of changing the power supply voltage.

3. The circuit of claim 2, wherein the voltage measurement unit comprises:

a voltage dividing unit configured to be connected between the high voltage pin and the reference ground for dividing a voltage at the high voltage pin; and

and a measurement unit configured to be connected to the voltage division unit for turning on or off measurement of the power supply voltage via measurement of the divided voltage of the voltage at the high voltage pin according to the second control signal.

4. The circuit of claim 3, wherein the operating current is a time-varying current,

wherein the current limiting unit has the operating current and the measuring unit stops the measurement of the supply voltage in case the first control unit turns on the connection between the high voltage pin and the power supply pin;

in case the first control unit disconnects the high voltage pin from the power supply pin, the current limiting unit has a current at least a first order of magnitude smaller than the operating current, and the measurement unit starts the measurement of the supply voltage.

5. The circuit of claim 4, wherein the voltage dividing unit comprises:

a first voltage dividing unit configured to be connected between the high voltage pin and a first node; and

a second voltage dividing unit configured to be connected between the first node and the reference ground,

wherein the voltage at the first node is a divided voltage of the voltage at the high voltage pin.

6. The circuit of claim 5, wherein the measurement unit comprises:

a first switch configured to be connected between the first node and a measurement terminal for being turned on or off according to the second control signal to measure the partial pressure via the measurement terminal with the first switch turned on; and

and a storage unit configured to be connected between the measurement terminal and the reference ground, for storing the partial pressure measured via the measurement terminal in a case where the first switch is turned on, and for holding the measured partial pressure at the measurement terminal in a case where the first switch is turned off.

7. The circuit of claim 6, the circuit further comprising:

a second control unit configured to be connected between the high voltage pin and the first control unit for turning on or off the power supply of the power supply terminal to the energy storage device via the high voltage pin according to a power supply signal,

the first control unit is configured to be connected between the second control unit and the power supply pin, and is used for switching on or switching off connection between the high-voltage pin and the power supply pin according to the first control signal under the condition that the second control unit starts the power supply end to supply power to the energy storage device through the high-voltage pin.

8. The circuit of claim 7, further comprising:

a signal generation unit configured to generate the first control signal and the second control signal as pulse width modulation signals,

wherein the energy storage device is a first capacitor connected between the power pin and the reference ground,

wherein the first control unit is a second switch which is switched on or off according to the first control signal,

the first control signal has a predetermined duty cycle, and the predetermined duty cycle is such that the variation of the voltage across the first capacitor is smaller than a first predetermined value during the period when the second switch is turned off according to the first control signal.

9. The circuit of claim 8, wherein the first switch and the second switch are switches having the same on level, and the first control signal and the second control signal are inverted signals.

10. The circuit of claim 8, wherein the current limiting unit is a first resistor having a first resistance value,

wherein the first voltage dividing unit is a second resistor with a second resistance value, the second voltage dividing unit is a third resistor with a third resistance value, the sum of the second resistance value and the third resistance value is at least a second order of magnitude larger than the first resistance value,

wherein the memory cell is a second capacitor.

11. The circuit of any one of claims 1-10, wherein the LED control chip is for an LED drive circuit for converting current of an external power supply line to a constant current to power an LED,

wherein the power supply terminal is a terminal of the external power supply line for connection to the LED control chip, or a predetermined terminal of the LED drive circuit capable of supplying the power supply voltage to the LED control chip,

wherein the average voltage value of the power supply voltage is greater than the second voltage value.

12. The circuit of claim 11, wherein the predetermined terminal is a drain of a constant current switch of the LED driving circuit,

wherein the grid electrode of the constant current switch is connected to a constant current control module of the LED control chip, the drain electrode of the constant current switch is connected to a first output terminal of the LED drive circuit via a diode and is connected to a second output terminal of the LED drive circuit via an inductor, the source electrode of the constant current switch is connected to the reference ground,

wherein the external power supply line is connected to the first output terminal, and the first output terminal and the second output terminal are used for connecting the LED.

13. The circuit of claim 11, wherein the LED driving circuit has a power factor greater than a predetermined value.