Low-voltage supply in control gear for lamps

Abstract

Circuit (101) for the low-voltage power supply of an integrated circuit of an operating device (100) for lighting means (116), comprising: - a storage capacitor (106); - wherein the circuit (101) is supplied with a supply voltage derived from an AC voltage, and the circuit (101) is designed to provide a feedback-regulated output voltage at the storage capacitor (106), characterized in that: the circuit (101) is designed to provide a higher output voltage in a first temperature range in which a temperature of the circuit (101) and in particular of the storage capacitor (106) is less than a threshold value than in a second temperature range which is higher than the first temperature range, wherein the circuit (101) further comprises a temperature-dependent resistor (110) which is arranged in a feedback path for a signal representing the output voltage to a low-voltage supply (109).

Description

1. Field of the invention

[0001] The present invention relates to the field of so-called low-voltage power supplies, also called low-voltage voltage supplies, in particular for lighting control devices, such as electronic ballasts for drivers of LED modules (LEDs, OLEDs). 2. Background

[0002] A low-voltage power supply is a circuit arrangement that can generate a DC voltage supply in an operating device within a voltage range suitable for the supply voltage of (active) electronic components (integrated circuits, microcontrollers, ASICs, etc.). These DC supply voltages are typically in the range below 15 volts DC.

[0003] LED drivers are often required to start at temperatures of around -25°C in indoor applications and around -40°C in outdoor applications. One of the critical components at these temperatures is the low-voltage power supply. In low-voltage power supplies, energy is usually stored in an electrolytic capacitor at the circuit output. However, this capacitor has the property that its equivalent series resistance (ESR), also known as equivalent resistance, increases sharply at low temperatures. As a result, a ripple on the low-voltage voltage applied to the capacitor increases. This voltage ripple can become so large that the low-voltage voltage drops below the threshold of the components to be supplied. To prevent this, several capacitors can be connected in parallel. However, connecting capacitors in parallel increases the component complexity.The capacitance actually required to keep the voltage ripple low at room temperature can be chosen relatively small. If the low-voltage voltage is increased, the losses in the loads being supplied also increase.

[0004] Therefore, the low-voltage power supply typically includes a storage capacitor whose temperature characteristics are such that the ripple it is designed to filter may no longer be adequately filtered at very low temperatures. If the low-voltage power supply outputs a supply voltage at or just above a nominal value of, for example, 12 volts to a microcontroller or ASIC (as an example of a controller), the problem can arise that, in certain valleys of the voltage ripple, a minimum value of the controller's supply voltage is undershot, causing the controller to no longer receive sufficient power and thus enter a defined "shutdown / lockdown" state.

[0005] For example, DE 10 2013 216 878 A1 shows a two-stage clocked electronic energy converter for transmitting electrical power, having a first terminal for connecting an electrical energy source, a second terminal for connecting a consumer and an intermediate circuit capacitor, wherein a first stage of the two-stage clocked electronic energy converter has a first converter in boost mode, which converts an electrical voltage at the first terminal into an electrical intermediate circuit voltage at the intermediate circuit capacitor, and wherein the intermediate circuit capacitor supplies a second stage of the two-stage clocked electronic energy converter, which supplies the consumer with electrical energy in a controllable manner.The energy converter has a control unit which is designed to adjust the power drawn from the intermediate circuit capacitor by the second stage in such a way that an instantaneous minimum of the intermediate circuit voltage caused by the power draw is greater than a predetermined voltage comparison value.

[0006] Furthermore, document DE 10 2008 017 557 A1 discloses an operating device for lamps, in particular for a low-voltage gas discharge lamp. The operating device comprises a control unit that controls the supply of electrical power to the lamps, an integrated circuit for operating the control unit, a low-voltage unit that supplies at least the IC with low-voltage voltage, and an interface via which external control signals for operating the lamps can be supplied to the IC. External power is supplied to the integrated circuit via the interface during the start-up phase of the low-voltage unit.

[0007] Furthermore, US 2016 / 0 323 957 A1 describes a lighting device including a solid-state light source, such as an LED light source. A control module of the lighting device uses a temperature sensing circuit to determine a relative ambient temperature. If the ambient temperature is above a defined threshold, a drive signal is delivered to the solid-state light source with a target drive level corresponding to a normal light output level. If the ambient temperature is below the ambient temperature threshold, the drive signal is delivered to the semiconductor light source with a reduced drive level that is lower than the target drive level.

[0008] Furthermore, document CN 1 11 867 184 A relates to a low-temperature starting device of an LED driver comprising a voltage supply VCC, a control optocoupler, a current-limiting resistor, an operational amplifier and an LED controller output current control circuit, wherein one end of the control optocoupler is connected to the voltage supply VCC via the current-limiting resistor, the other end of the control optocoupler is connected to the output end of the operational amplifier and the input end of the operational amplifier is connected to the LED controller output current control circuit;When the LED driver is started, the LED controller output current control circuit controls the operational amplifier to reduce the output current of the LED driver, so that the LED driver operates at low power, and after the set time is reached, the LED controller output current control circuit controls the operational amplifier to output the output current of the LED driver normally, so that the LED driver operates at the set normal power.;

[0009] It is therefore an object of the present invention to improve the low-temperature behavior of a low-voltage power supply.

[0010] These and other objects, which will be mentioned upon reading the following description or which may be recognized by a person skilled in the art, are achieved by the subject matter of the independent claims. The dependent claims develop the central idea of the present invention in a particularly advantageous manner. 3. Detailed description of the invention

[0011] According to a first aspect, the invention relates to a circuit for the low-voltage power supply of an integrated circuit of an operating device for lighting devices. The circuit comprises a storage capacitor, and a supply voltage derived from an AC voltage is supplied to the circuit. Furthermore, the circuit is designed to provide a feedback-regulated output voltage at the storage capacitor and to provide a higher output voltage in a first temperature range, in which a temperature of the circuit, and in particular of the storage capacitor, is lower than a threshold value, than in a second temperature range, which is higher than the first temperature range.

[0012] This has the advantage that even at very low temperatures of, for example, below -20 degrees Celsius, it can be ensured that the valleys of the ripple do not fall below the minimum value for the supply voltage, thus preventing the controller from switching off.

[0013] According to the first aspect, the circuit further comprises a temperature-dependent resistor arranged in a return path for a signal representing the output voltage to a low-voltage supply.

[0014] This has the advantage that a temperature-dependent resistor can be used to increase the low-voltage voltage, thus compensating for higher ripple by temporarily increasing the low-voltage voltage. Furthermore, this has the advantage that during the start-up phase of the converter's operation, the setpoint for the supply voltage, which is controlled by a control loop, is selectively increased.

[0015] According to one embodiment, the resistor is a PTC thermistor or a thermistor and the resistor is arranged such that it experiences substantially the same temperature as the storage capacitor.

[0016] This has the advantage that an increase in the low voltage can be realized by a temperature-dependent resistor and thus a higher ripple can be compensated by a temporary increase in the low voltage.

[0017] According to one embodiment, the circuit is designed to increase the output voltage in a time-dependent manner, for example in a period of time between 10 seconds and one minute, preferably between 20 seconds and 50 seconds, after the start of operation of the circuit.

[0018] According to one embodiment, the circuit further comprises a clamping diode, wherein the clamping diode is designed to prevent the output voltage from exceeding a threshold value.

[0019] This has the advantage that the circuit is protected from overvoltage.

[0020] According to one embodiment, the circuit comprises a resistor arranged in series with the storage capacitor.

[0021] According to one embodiment, the storage capacitor is an electrolytic capacitor.

[0022] This has the advantage that electrolytic capacitors offer higher capacitance for a given volume than other capacitor technologies. Furthermore, properly specified electrolytic capacitors can achieve a service life of more than 20 years in demanding industrial applications.

[0023] According to a second aspect, the invention relates to an operating device for lighting means, comprising a circuit according to the first aspect and at least one control unit supplied by the circuit.

[0024] According to one embodiment, the control unit is a microcontroller or an ASIC.

[0025] According to one embodiment, the operating device has an actively clocked PFC circuit, wherein the output voltage of the PFC circuit represents the supply voltage of the circuit for the low-voltage power supply of an integrated circuit.

[0026] According to one embodiment, the operating device has a primary-side clocked isolated or non-isolated DC / DC converter supplied by the output voltage of the PFC circuit for supplying a light source.

[0027] This has the advantage of increasing the power factor and improving harmonic distortion.

[0028] According to one embodiment, in the operating device, the circuit for the low-voltage power supply of an integrated circuit is arranged on the primary side of the isolated converter.

[0029] According to one embodiment of the operating device, the circuit for the low-voltage power supply of an integrated circuit is arranged on the secondary side of the isolated converter.

[0030] According to one embodiment of the operating device, the control unit is a control unit for clocking a switch and / or the control unit is designed for communication with an interface of the operating device.

[0031] According to a third aspect, the invention relates to a method for the low-voltage power supply of an integrated circuit of an operating device for lighting devices by means of a circuit, comprising: supplying a supply voltage derived from an AC or DC voltage to a circuit; providing a regulated output voltage at a storage capacitor; wherein the circuit is designed to provide a higher output voltage in a first temperature range, in which a temperature of the circuit and in particular of the storage capacitor is lower than a threshold value, than in a second temperature range, which is higher than the first temperature range, wherein the circuit further comprises a temperature-dependent resistor, which is arranged in a return path for a signal representing the output voltage to a low-voltage supply. 4. Short description of the characters

[0032] Below is a brief description of the figures. It shows: Fig. 1 is a schematic diagram of a circuit for the low-voltage power supply of an integrated circuit of an operating device for lamps according to a preferred embodiment; and Fig. 2 a schematic representation of a method for low-voltage power supply of an integrated circuit of an operating device for lamps by means of a circuit according to an embodiment. 5. Detailed description

[0033] Fig. 1 shows a schematic representation of a circuit 101 for the low-voltage power supply of an integrated circuit of an operating device 100 for lighting means 116 according to a preferred embodiment.

[0034] According to this embodiment, the illustrated circuit 101 is powered by the output voltage of a PFC circuit. This output voltage typically exhibits a ripple, for example, at the frequency of a rectified mains voltage.

[0035] However, circuit 101 can also be derived from other DC voltages in a lighting control device, especially those that are subject to ripple. Preferably, circuit 101 is powered from a voltage on the primary side of an isolated or non-isolated DC / DC converter for supplying a lighting device.

[0036] The circuit 101 comprises a storage capacitor 106, wherein the circuit 101 is supplied with a supply voltage derived from an AC voltage, and the circuit 101 is configured to provide a regulated output voltage at the storage capacitor 106. Furthermore, the circuit 101 is configured to provide a higher output voltage in a first temperature range, in which a temperature of the circuit 101, and in particular of the storage capacitor 106, is less than a threshold value, than in a second temperature range, which is higher than the first temperature range.

[0037] In one embodiment, during a start-up phase of converter operation, the setpoint for the supply voltage, which is controlled by a control loop, is selectively raised. This can be achieved, for example, by a temperature-dependent resistor 110 changing the setpoint or the feedback value of the control loop of the low-voltage supply 109.

[0038] Preferably, the temperature-dependent resistor 110 is arranged such that it experiences substantially the same temperature as the aforementioned storage capacitor 106.

[0039] With increasing operation, for example, between 10 seconds and 1 minute, the ripple on the storage capacitor 106 will decrease.

[0040] As the capacitor heats up, the series resistance 105 decreases, and the ripple decreases again. Thus, the increase in the supply voltage can be limited to a time range between 10 seconds and one minute, preferably between 20 seconds and 50 seconds. Preferably, this increase in the supply voltage for a cold start is designed to be active only until the temperature at the storage capacitor has increased by 20 degrees relative or above a temperature of, for example, -20 degrees (absolute).

[0041] Furthermore, so-called clamping diodes 107 can be provided in the circuit 101 to ensure that the supply voltage does not inadvertently exceed a specified range. If this limit is exceeded, these clamping diodes 107 draw additional current from the storage capacitor 106, which contributes to the heating of the storage capacitor 106.

[0042] The higher ripple can be compensated for by temporarily increasing the low-voltage voltage. This increase in the low-voltage voltage can be achieved, for example, using the temperature-dependent resistor 110. Once the device has warmed up, the temperature rises due to the losses within the device, and the low-voltage voltage can then drop again.

[0043] Preferably, the low-voltage power supply 109 is an LVPS (low-voltage power supply) and normally supplies, for example, 12V. At low temperatures, a feedback 113 can be manipulated so that the low-voltage power supply 109 supplies a slightly higher voltage (e.g., 15V). Many components can have an undervoltage lockout. To prevent this from being reached at low temperatures, the capacitance of the storage capacitor 106 can be selected accordingly large, or an electrolytic capacitor (electrolytic capacitor) with a low equivalent series resistance 105 (ESR, hybrid electrolytic capacitor) can be selected.

[0044] For 15V operation, several clamping diodes (107) are preferably provided to protect against overvoltage. If the clamping becomes active / conducts, a small portion of the LVPS 15V voltage can be short-circuited, temporarily placing a larger load on the critical electrolytic capacitor. This causes the electrolytic capacitor to heat up, and the problem of excessive ESR is resolved automatically.

[0045] The operating device 100 for the lighting device 116 comprises the circuit 101 and at least one control unit 112 supplied by the circuit. The control unit 112 can be a microcontroller or an ASIC.

[0046] Furthermore, the operating device 100 can have an actively clocked PFC circuit 103, wherein the output voltage of the PFC circuit 103 represents the supply voltage of the circuit 101 for the low-voltage power supply of the integrated circuit.

[0047] For example, the circuit 100 for supplying low voltage power to the integrated circuit is arranged on the primary side of the isolated converter 104.

[0048] Alternatively, the circuit for supplying the low-voltage power to the integrated circuit can also be arranged on the secondary side of the isolated converter 104.

[0049] The operating device 100 may further comprise an interface 111, wherein the control unit 112 is designed to clock a switch and / or to communicate with the interface 111 of the operating device 100.

[0050] The operating device 100 may further include an electromagnetic interference (EMI) filter and a rectifier 102.

[0051] Furthermore, a unit for sampling and rectifying the current 114 and a filter unit 115 can be arranged on the secondary side of the operating device 100.

[0052] Fig.2 shows a schematic representation of a method 200 for low-voltage power supply of an integrated circuit of an operating device 100 for lighting means 116 by means of a circuit 101 according to an embodiment.

[0053] The low-voltage power supply method 200 includes the following steps: - supplying 201 a supply voltage derived from an AC or DC voltage to a circuit 101; - Providing 202 a regulated output voltage at a storage capacitor 106, wherein the circuit 101 is designed to provide a higher output voltage in a first temperature range in which a temperature of the circuit and in particular of the storage capacitor 106 is less than a threshold value than in a second temperature range which is higher than the first temperature range.

Claims

[1] Circuit (101) for the low-voltage power supply of an integrated circuit of an operating device (100) for lighting means (116), comprising: - a storage capacitor (106); - wherein the circuit (101) is supplied with a supply voltage derived from an AC voltage, and the circuit (101) is designed to provide a feedback-regulated output voltage at the storage capacitor (106) characterized byin that: the circuit (101) is designed to provide a higher output voltage in a first temperature range in which a temperature of the circuit (101) and in particular of the storage capacitor (106) is less than a threshold value than in a second temperature range which is higher than the first temperature range, wherein the circuit (101) further comprises a temperature-dependent resistor (110) which is arranged in a return path for a signal representing the output voltage to a low-voltage supply (109). [2] The circuit (101) of claim 1, wherein the resistor (110) is a PTC thermistor or a thermistor, and wherein the resistor (110) is arranged to experience substantially the same temperature as the storage capacitor (106). [3] Circuit (101) according to claim 1 or 2, wherein the low-voltage supply (109) is designed to increase the output voltage in a time-dependent manner, for example in a period of time between 10 seconds and one minute, preferably between 20 seconds and 50 seconds, after the start of operation of the circuit (101). [4] Circuit (101) according to one of the preceding claims, wherein the circuit further comprises a clamping diode (107), wherein the clamping diode (107) is designed to prevent exceeding a threshold value of the output voltage. [5] Circuit (101) according to one of the preceding claims, wherein the circuit (101) comprises a resistor (105) arranged in series with the storage capacitor (106). [6] Circuit (101) according to one of the preceding claims, wherein the storage capacitor (106) is an electrolytic capacitor. [7] Operating device (100) for lighting means (106), comprising a circuit (101) according to one of the preceding claims and at least one control unit (112) supplied by the latter. [8] Operating device (100) according to claim 7, wherein the control unit (112) is a microcontroller or an ASIC. [9] Operating device (100) according to one of claims 7 or 8, comprising an actively clocked PFC circuit (103), wherein the output voltage of the PFC circuit (103) represents the supply voltage of the circuit (101) for the low-voltage power supply of an integrated circuit. [10] Operating device (100) according to claim 9, comprising a primary-side clocked isolated or non-isolated DC / DC converter supplied by the output voltage of the PFC circuit (103). [11] Operating device (100) according to claim 9, wherein the circuit (101) for the low-voltage power supply of an integrated circuit is arranged on the primary side of the isolated converter. [12] Operating device (100) according to claim 9, wherein the circuit for the low-voltage power supply of an integrated circuit is arranged on the secondary side of the isolated converter. [13] Operating device (100) according to one of claims 7 to 12, wherein the control unit (112) is a control unit for clocking a switch and / or is designed for communication with an interface (111) of the operating device (100). [14] Method (200) for the low-voltage power supply of an integrated circuit of an operating device (100) for lighting means (116) by means of a circuit (101), comprising: - supplying (201) a supply voltage derived from an AC or DC voltage to the circuit (101); - providing (202) a regulated output voltage to a storage capacitor (106); characterized by in that: the circuit (101) is designed to provide a higher output voltage in a first temperature range in which a temperature of the circuit (101) and in particular of the storage capacitor (106) is less than a threshold value than in a second temperature range which is higher than the first temperature range, wherein the circuit (101) further comprises a temperature-dependent resistor (110) which is arranged in a return path for a signal representing the output voltage to a low-voltage supply (109).

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