Electric leakage detection circuit and LED drive circuit

Abstract

The invention provides an electric leakage detection circuit and an LED drive circuit, and the electric leakage detection circuit comprises a detection circuit which is connected between a high-potential end and a low-potential end of an input end, and the low-potential end of the input end is grounded; the control circuit controls the detection circuit to enter a discharge mode and then enter a detection mode after the input end is powered on, and in the discharge mode, the input end discharges to the ground through the detection circuit; in the detection mode, whether the input end leaks electricity or not is detected according to current flowing through the detection circuit. According to the electric leakage detection circuit provided by the invention, whether the input end leaks electricity or not is judged by detecting the current flowing through the detection circuit, and meanwhile, the detection circuit is multiplexed before electric leakage detection, so that the input end discharges electricity to the ground through the detection circuit. Therefore, the input end discharges electricity to the ground by multiplexing the detection circuit, interference of common-mode electric leakage of the input end on electric leakage detection is solved in a low-cost mode, no extra power consumption is added to the system, and the system efficiency is prevented from being reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of LED driving, and in particular relates to a leakage detection circuit and an LED driving circuit. Background Art

[0002] like Figure 1 As shown, taking full-wave detection as an example, in the prior art, the LED driving circuit with leakage detection function, when the LED driving circuit is operating normally, the rectifier circuit rectifies the AC input voltage, and the power conversion circuit converts the rectified voltage to drive the LED load. Before the LED driving circuit operates normally to supply power to the LED load, the leakage detection circuit detects whether the current flowing through the leakage detection circuit at the input end is greater than the threshold current. If not, it is determined that leakage occurs, and the LED driving circuit is controlled to be in the off state; if so, it is determined that no leakage occurs, and the LED driving circuit is controlled to operate normally.

[0003] However, the commonly used solution of generating pulses according to the input voltage to detect whether the input terminal is leaking is often affected by the common-mode leakage of the input terminal, resulting in the failure of leakage detection to be performed normally. When common-mode leakage occurs at the input terminal, the input terminal voltage increases (relative to the system reference ground), often resulting in the failure of leakage detection pulses to be generated, making leakage detection unable to be performed normally.

[0004] Regarding this issue, Figure 2 As shown in Figure 1, a resistor is often connected in parallel at the input to discharge the current, thereby reducing the impact of common-mode leakage. However, this solution increases the peripheral cost on the one hand, and the loss on the resistor also reduces the system efficiency on the other hand. Summary of the invention

[0005] In order to solve the technical problems of high cost and reduced system efficiency in the prior art of reducing the common-mode leakage of the input terminal by discharging current through a resistor in parallel at the input terminal, the present invention proposes a leakage detection circuit and an LED driving circuit, the leakage detection circuit comprising:

[0006] A detection circuit, wherein the detection circuit is connected between the high and low potential ends of the input end, and the low potential end of the input end is grounded;

[0007] The control circuit controls the detection circuit to enter the discharge mode first and then the detection mode after the input end is powered on.

[0008] Wherein, in the discharge mode, the input end discharges to the ground through the detection circuit;

[0009] In the detection mode, the control circuit detects whether the input end has leakage according to the current flowing through the detection circuit.

[0010] Furthermore, the detection circuit includes a first switch, which is connected between the high and low potential ends. In the discharge mode, the control circuit controls the first switch to be incompletely turned on, and in the detection mode, the control circuit controls the first switch to be fully turned on.

[0011] Furthermore, the control circuit comprises:

[0012] An input detection circuit detects whether the input voltage rises or drops to a preset voltage to output a pulse signal;

[0013] A first driving circuit generates a first driving signal according to the pulse signal to control the first switch to be fully turned on;

[0014] The second driving circuit generates a second driving signal at any time between the power-on time of the input terminal and the generation time of the pulse signal, so as to control the second switch to be partially turned on.

[0015] Furthermore, in the detection mode, when the current flowing through the detection circuit is greater than a threshold current, the detection circuit outputs a valid leakage detection signal.

[0016] When the detection circuit generates N valid leakage detection signals continuously, it indicates that there is no leakage at the input terminal, where N is a natural number greater than 0.

[0017] In one embodiment, when N is greater than 1, the detection circuit enters N discharge modes and N detection modes, wherein the detection circuit immediately enters the N discharge mode when the N-1 detection mode ends, and immediately enters the N detection mode when the N discharge mode ends.

[0018] In another embodiment, when N is greater than 1, the detection circuit enters N discharge modes and N detection modes, wherein after the N-1th detection mode ends, the detection circuit enters the Nth discharge mode after a first delay time, and enters the Nth detection mode immediately after the Nth discharge mode ends.

[0019] Furthermore, the second driving circuit includes a first operational amplifier, a control switch and a logic circuit.

[0020] The first input terminal of the first operational amplifier receives a sampling voltage, the second terminal of the first operational amplifier receives a reference voltage, and the output terminal of the first operational amplifier is connected to the control terminal of the first switch through the control switch.

[0021] The logic circuit controls the on and off of the control switch according to the leakage detection signal and / or the pulse signal, wherein the sampling voltage represents the current flowing through the first switch, and the leakage detection signal represents the relationship between the current flowing through the detection circuit and the threshold current.

[0022] In one embodiment, the logic circuit comprises:

[0023] A counting unit, for counting the leakage detection signal to output a counting signal;

[0024] a first logic unit, performing logic processing on the counting signal to output a first logic signal, and the first driving circuit stops outputting the pulse signal according to the first logic signal;

[0025] The second logic unit performs logic processing on the first logic signal to output a control signal for the control switch.

[0026] In another embodiment, the logic circuit comprises:

[0027] A counting unit, for counting the leakage detection signal to output a counting signal;

[0028] a first logic unit, performing logic processing on the counting signal to output a first logic signal, and the first driving circuit stops outputting the pulse signal according to the first logic signal;

[0029] The second logic unit performs delay processing according to the changing edge of the pulse signal to output a delay signal, and performs logic processing on the delay signal and the first logic signal to output a control signal for the control switch.

[0030] An LED driving circuit comprises the leakage detection circuit mentioned above.

[0031] In the leakage detection circuit proposed by the present invention, the current flowing through the detection circuit is detected to determine whether the input terminal is leaking, and the detection circuit is reused before the leakage detection is performed to discharge the input terminal to the ground through the detection circuit. Thus, by reusing the detection circuit to discharge the input terminal to the ground, the problem of common-mode leakage at the input terminal affecting leakage detection is solved at a relatively low cost, and additional power consumption is not added to the system, thereby avoiding reducing system efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 and Figure 2 It is a structural block diagram of an existing leakage detection circuit;

[0033] Figure 3 It is a structural block diagram of the leakage detection circuit proposed by the present invention;

[0034] Figure 4 A further detailed structural block diagram of the leakage detection circuit proposed in the present invention;

[0035] Figure 5 is a structural block diagram of a second driving circuit;

[0036] Figure 6 The specific circuit structure of the second driving circuit in the first embodiment;

[0037] Figure 7 is a waveform diagram in the first embodiment;

[0038] Figure 8 is a specific circuit structure of the second driving circuit in the second embodiment;

[0039] Fig. 9 It is a waveform diagram in the second embodiment. DETAILED DESCRIPTION

[0040] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0041] Based on the background technology, the technology of discharging by connecting a resistor in parallel at the input end to reduce the influence of common-mode leakage at the input end has the problems of high cost and reduced system efficiency. The present invention proposes a leakage detection circuit applied to an LED driving circuit, such as Figure 3 As shown, including:

[0042] The detection circuit is connected between the high and low potential ends of the input end, and the low potential end of the input end is grounded;

[0043] The control circuit, after the input end is powered on, controls the detection circuit to first enter the discharge mode and then the detection mode, where:

[0044] In the discharge mode, the input terminal discharges to the ground through the detection circuit;

[0045] In the detection mode, the control circuit detects whether there is leakage at the input terminal according to the current flowing through the detection circuit.

[0046] It can be seen that in the leakage detection circuit proposed by the present invention, the current flowing through the detection circuit is detected to determine whether the input terminal is leaking, and the detection circuit is reused before the leakage detection is performed to discharge the input terminal to the ground through the detection circuit. Therefore, by reusing the detection circuit to discharge the input terminal to the ground, the problem of common-mode leakage at the input terminal affecting leakage detection is solved at a relatively low cost, and additional power consumption will not be added to the system, thereby avoiding reducing system efficiency.

[0047] Further, such as Figure 4As shown, the detection circuit includes a first switch Q1 and a sampling resistor Rcs, and the first switch Q1 and the sampling resistor Rcs are connected in series between the high and low potential ends of the input end. In the discharge mode, the control circuit controls the first switch Q1 to be incompletely turned on, so that the input end discharges the charge to the ground with a small current through the first switch Q1, thereby reducing the influence of the common-mode leakage of the input end. In the detection mode, the control circuit controls the first switch Q1 to be fully turned on, so as to determine whether the input end is leaking by detecting the magnitude relationship between the current flowing through the first switch Q1 and the threshold current.

[0048] Further, such as Figure 4 As shown, the control circuit includes an input detection circuit, which outputs a pulse signal when it detects that the input voltage rises or drops to a threshold voltage; a first drive circuit, which generates a first drive signal VG1 according to the pulse signal to drive the first switch Q1 to be fully turned on; and a second drive circuit, which generates a second drive signal VG2 at any time between the power-on moment of the input terminal and the pulse signal generation moment to control the first switch Q1 to be incompletely turned on, and the second drive signal VG2 is smaller than the first drive signal VG1.

[0049] Theoretically, when the current flowing through the first switch in the detection mode is greater than the threshold current, it can be determined that there is no leakage at the input terminal. However, a single detection may result in a misjudgment. In order to improve the accuracy of leakage detection, it is preferred to enter the detection mode multiple times within a period of time. If the current flowing through the first switch is detected to be greater than the threshold current in each detection mode, it is determined that there is no leakage at the input terminal.

[0050] In one embodiment, if Figure 5 As shown, the input detection circuit sends out a pulse signal when it detects that the input voltage Vrec is first lower than VL and then higher than VH. When the first drive circuit receives the pulse signal, it outputs the first drive signal VG1 to control the first switch Q1 to be fully turned on, thereby performing leakage detection. When the sampling voltage Vcs is greater than the threshold voltage Vth, the comparator COMP1 outputs a leakage detection signal Leak (high level signal) in a valid state; when the sampling voltage Vcs is less than the threshold voltage Vth, the comparator COMP1 outputs a leakage detection signal Leak (low level signal) in an invalid state. The second drive circuit includes a first operational amplifier U1, a control switch K1, and a logic circuit. The first input terminal of the first operational amplifier U1 is connected to the sampling resistor Rcs, the second input terminal receives the reference voltage Vref, and the output terminal is connected to the control terminal of the first switch Q1 through the control switch K1. The logic circuit controls the on and off of the control switch K1 according to the leakage detection signal Leak output by the comparator COMP1. Specifically, as Figure 6As shown, in this embodiment, when the input end is powered on, the first switch Q1 is turned off, and the comparator COMP1 outputs a leakage detection signal Leak in an invalid state. At this time, the counting unit counts zero times, the first logic unit outputs a first logic signal in a low level state, and the second logic unit inverts the first logic signal to drive the control switch K1 to turn on, so that the first operational amplifier U1 drives the first switch Q1 to be partially turned on. After power-on, the input detection circuit detects the input voltage Vrec. When the input voltage Vrec rises to VH, a pulse signal is output. The first drive circuit outputs a first drive signal VG1 according to the pulse signal to drive the first switch Q1 to be fully turned on. When the first switch Q1 is fully turned on, the comparator COMP1 outputs a leakage detection signal Leak according to Vcs and Vth. If the leakage detection signal Leak is in a valid state, the counting signal output by the counting unit indicates that it is counted once. The first drive signal VG1 controls the turn-on time of the first switch Q1 to be preset, that is, after the preset time, the first switch Q1 returns to an incompletely turned-on state. When waiting for the next input cycle to come, repeat the above process until the counting signal output by the counting unit indicates N consecutive counts, then the first logic unit outputs the first logic signal in a high level state, and the first drive unit and the second logic unit control the first drive signal VG1 to stop generating and control the switch K1 to disconnect according to the first logic signal in a high level state, so that the first switch Q1 is disconnected, and the leakage detection circuit ends its work. In a certain input cycle, the comparator COMP1 outputs the leakage detection signal Leak in an invalid state, then the counting unit counts to zero and determines that the input terminal is leaking. After that, the leakage detection circuit repeats the above working process. That is, if Figure 7 As shown, in this embodiment, within a period of time, the leakage detection circuit enters the discharge mode and the detection mode N times, there is no delay between two adjacent detection modes and discharge modes, and the N-1th detection mode is immediately entered when the N-1th detection mode ends, and the Nth detection mode is immediately entered when the Nth discharge mode ends, that is, during this period of time, except for the detection mode, the leakage detection circuit is in the discharge mode.

[0051] It should be noted that the first logic unit and the second logic unit can be implemented by triggers, logic gates, etc. It is easy for those skilled in the art to think of how to specifically set the first logic unit and the second logic unit based on the known working principle.

[0052] In another embodiment, if Figure 5 and Figure 8As shown, the input detection circuit sends out a pulse signal when it detects that the input voltage Vrec is first lower than VL and then higher than VH. When the first drive circuit receives the pulse signal, it outputs the first drive signal VG1 to control the first switch Q1 to be fully turned on, thereby performing leakage detection. When the sampling voltage Vcs is greater than the threshold voltage Vth, the comparator COMP1 outputs a leakage detection signal Leak (high level signal) in a valid state; when the sampling voltage Vcs is less than the threshold voltage Vth, the comparator COMP1 outputs a leakage detection signal Leak (low level signal) in an invalid state. The second drive circuit includes a first operational amplifier U1, a control switch K1, and a logic circuit. The first input terminal of the first operational amplifier U1 is connected to the sampling resistor Rcs, the second input terminal receives the reference voltage Vref, and the output terminal is connected to the control terminal of the first switch Q1 through the control switch K1. The logic circuit controls the on and off of the control switch K1 according to the leakage detection signal Leak and the pulse signal (a single pulse pulse is sent externally when power is on, and a pulse signal is sent after power is on). As shown Figure 8As shown, in this embodiment, when the input end is powered on, the first switch Q1 is turned off, and the comparator COMP1 outputs a leakage detection signal Leak in an invalid state. At this time, the counting unit counts zero times, the first logic unit outputs a first logic signal in a low level state, and the second logic unit receives a single pulse pulse and then performs logic processing to drive the control switch K1 to turn on, so that the first operational amplifier U1 drives the first switch Q1 to be partially turned on. After power-on, the input detection circuit detects the input voltage Vrec. When the input voltage Vrec rises to VH, it outputs a pulse signal. The first drive circuit outputs a first drive signal VG1 according to the pulse signal to drive the first switch Q1 to be fully turned on. When the first switch Q1 is fully turned on, the comparator COMP1 outputs a leakage detection signal Leak according to Vcs and Vth. If the leakage detection signal Leak is in a valid state, the counting signal output by the counting unit indicates that it is counted once. The first drive signal VG1 controls the turn-on time of the first switch Q1 to be preset, that is, after the preset time, the first switch Q1 returns to an incompletely turned-on state. At this time, the second logic unit triggers the delay according to the falling edge of the pulse signal, outputs the delay signal after the delay Td, and then performs logic processing on the delay signal and the first logic signal to drive the control switch K1 to turn on, so that it enters the discharge mode after a delay of Td after the detection mode ends. When waiting for the next input cycle to come, the above process is repeated until the counting signal output by the counting unit indicates N consecutive counts, then the first logic unit outputs the first logic signal in the high-level state, and the first drive unit and the second logic unit control the first drive signal VG1 to stop generating and control the switch K1 to disconnect according to the first logic signal in the high-level state, so that the first switch Q1 is disconnected, and the leakage detection circuit ends its work. In a certain input cycle, the comparator COMP1 outputs the leakage detection signal Leak in the invalid state, then the counting unit counts to zero and determines that the input end is leaking. Thereafter, the leakage detection circuit repeats the above working process. That is, if Fig. 9 As shown, in this embodiment, within a period of time, the leakage detection circuit enters N discharge modes and detection modes, and enters the N discharge mode after a delay of Td when the N-1 detection mode ends, and enters the N detection mode immediately when the N discharge mode ends.

[0053] When the leakage detection circuit detects leakage at the input end, the leakage fault is eliminated, the LED drive circuit is turned off and no power is supplied to the LED load; when the leakage detection circuit detects that the LED drive circuit has no leakage, the LED drive circuit operates and the output is constant to supply power to the LED load.

[0054] It should be noted that the above two embodiments only specifically list two situations in which the discharge mode and the detection mode are operated within a period of time, and do not represent a limitation on the operation process. In other embodiments, as long as it is ensured that the input terminal is discharged to the ground before each leakage detection, the remaining other time can be arbitrarily arranged for the input terminal to discharge to the ground or the first switch to be disconnected. At the same time, in the above two embodiments, the input detection circuit detects the rising change of the input voltage, but in other embodiments, the falling change can also be detected. In addition, in the above two embodiments, the leakage detection circuit is connected after the rectifier circuit, which is full-wave sampling. However, one end of the leakage detection circuit is connected to either end of the input terminal (L end or N end), and the other end is connected to the low potential end of the rectifier circuit, which is half-wave sampling.

[0055] The present invention further provides an LED driving circuit, which includes the leakage detection circuit provided above.

[0056] It should be noted that the specific implementation and corresponding illustrations given are merely a way of describing the implementation method of the present invention, and do not limit the specific structure of the implementation scheme of the present invention. Various changes or modifications can be made to these implementation schemes without departing from the principle and essence of the present invention, but these changes and modifications fall within the scope of protection of the present invention.

[0057] Although the embodiments are described and illustrated separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments can be replaced and integrated. If the content is not clearly recorded in one of the embodiments, reference can be made to another recorded embodiment.

[0058] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A leakage detection circuit, characterized in that: include: A detection circuit, wherein the detection circuit is connected between the high and low potential ends of the input end, and the low potential end of the input end is grounded; The control circuit controls the detection circuit to enter the discharge mode first and then the detection mode after the input end is powered on. Wherein, in the discharge mode, the input end discharges to the ground through the detection circuit; In the detection mode, the control circuit detects whether the input end has leakage according to the current flowing through the detection circuit.

2. The leakage detection circuit according to claim 1, characterized in that: The detection circuit includes a first switch, which is connected between the high and low potential ends. In the discharge mode, the control circuit controls the first switch to be incompletely turned on, and in the detection mode, the control circuit controls the first switch to be fully turned on.

3. The leakage detection circuit according to claim 2, characterized in that: The control circuit comprises: An input detection circuit detects whether the input voltage rises or drops to a preset voltage to output a pulse signal; A first driving circuit generates a first driving signal according to the pulse signal to control the first switch to be fully turned on; The second driving circuit generates a second driving signal at any time between the power-on time of the input terminal and the generation time of the pulse signal, so as to control the second switch to be partially turned on.

4. The leakage detection circuit according to claim 1, characterized in that: In the detection mode, when the current flowing through the detection circuit is greater than the threshold current, the detection circuit outputs a valid leakage detection signal. When the detection circuit generates N valid leakage detection signals continuously, it indicates that there is no leakage at the input terminal, where N is a natural number greater than 0.

5. The leakage detection circuit according to claim 4, characterized in that: When N is greater than 1, the detection circuit enters N discharge modes and N detection modes, wherein the detection circuit enters the N discharge mode immediately when the N-1 detection mode ends, and enters the N detection mode immediately when the N discharge mode ends.

6. The leakage detection circuit according to claim 4, characterized in that: When N is greater than 1, the detection circuit enters N discharge modes and N detection modes, wherein after the N-1th detection mode ends, the circuit enters the Nth discharge mode after a first delay time, and enters the Nth detection mode immediately after the Nth discharge mode ends.

7. The leakage detection circuit according to claim 3, characterized in that: The second driving circuit includes a first operational amplifier, a control switch and a logic circuit. The first input terminal of the first operational amplifier receives a sampling voltage, the second terminal of the first operational amplifier receives a reference voltage, and the output terminal of the first operational amplifier is connected to the control terminal of the first switch through the control switch. The logic circuit controls the on and off of the control switch according to the leakage detection signal and / or the pulse signal, wherein the sampling voltage represents the current flowing through the first switch, and the leakage detection signal represents the relationship between the current flowing through the detection circuit and the threshold current.

8. The leakage detection circuit according to claim 7, characterized in that: The logic circuit comprises: A counting unit, which counts the leakage detection signal to output a counting signal; a first logic unit, performing logic processing on the counting signal to output a first logic signal, and the first driving circuit stops outputting the pulse signal according to the first logic signal; The second logic unit performs logic processing on the first logic signal to output a control signal for the control switch.

9. The leakage detection circuit according to claim 7, characterized in that: The logic circuit comprises: A counting unit, which counts the leakage detection signal to output a counting signal; a first logic unit, performing logic processing on the counting signal to output a first logic signal, and the first driving circuit stops outputting the pulse signal according to the first logic signal; The second logic unit performs delay processing according to the changing edge of the pulse signal to output a delay signal, and performs logic processing on the delay signal and the first logic signal to output a control signal for the control switch.

10. An LED driving circuit, characterized in that: The invention comprises the leakage detection circuit as described in any one of claims 1 to 9.

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