DE102020132732A1 - Low-voltage supply in operating devices for lamps - Google Patents

Abstract

The present invention relates to a circuit for the low-voltage power supply of an integrated circuit of an operating device for lighting means, comprising: a storage capacitor; and wherein the circuit is supplied with a supply voltage derived from an AC voltage, and the circuit is designed to provide a regulated output voltage at the storage capacitor. The circuit is also 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 that is higher than the first temperature range.

Description

1. Field of the Invention

The present invention relates to the field of the so-called low-voltage supply, also known as low-voltage power supply, in particular for lamp operating devices, such as electronic ballasts for drivers of LED modules (LEDs, OLEDs).

2. Background

A low-voltage supply is a circuit arrangement that can be used to generate a DC voltage supply in an operating device in a voltage range that is suitable for the supply voltage of (active) electronic components (integrated circuits, microcontrollers, ASICs, etc.). Typically, these DC supply voltages range below 15 volts DC.

It is often a requirement for LED drivers for indoor applications to start at temperatures of around -25°C and for outdoor applications at around -40°C. One of the critical assemblies at these temperatures is the low-voltage supply. In the low-voltage supply, energy is mostly stored in an electrolytic capacitor at the output of the circuit. However, this has the property that its equivalent series resistance (ESR), also known as equivalent resistance, increases sharply at low temperatures. As a result, a ripple increases on the low-voltage applied to the capacitor. This voltage ripple can become so large that the low-voltage voltage falls below the threshold value 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 small at room temperature can be chosen to be relatively small. If the low-voltage voltage increases, the losses in the consumers to be supplied also increase.

A storage capacitor is therefore typically provided in the low-voltage supply, the temperature properties of which are such that a ripple to be filtered by it may no longer be adequately filtered at very low temperatures. If the low-voltage supply now outputs a supply voltage at or just above a nominal value of, for example, 12 volts to a microcontroller or ASIC (as an example for a controller), the problem can arise that the supply voltage of the controller falls below a minimum value in certain troughs of the voltage ripple, whereby the controller is no longer sufficiently supplied and can thus enter a defined or "shutdown/lockdown" state.

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

These and other objects that may be mentioned or recognized by a person skilled in the art upon reading the following description are solved 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

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 means. The circuit includes a storage capacitor and the circuit is supplied with a supply voltage derived from an AC voltage. 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 that is higher than the first temperature range.

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

According to one embodiment, the circuit further comprises a temperature-dependent resistor, which is arranged in a return path for a signal representing the output voltage to the low-voltage supply.

This has the advantage that the low-voltage can be increased by a temperature-dependent resistor, and a higher ripple can thus be compensated for by a temporary increase in the low-voltage. Furthermore, this has the advantage that during a starting phase of the operation of the converter, the desired value for the supply voltage, which is regulated by a control loop, is selectively increased.

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

This has the advantage that the low-voltage can be increased by a temperature-dependent resistor, and a higher ripple can thus be compensated for by a temporary increase in the low-voltage.

According to one embodiment, the circuit is designed to increase the output voltage as a function of time, for example in a period of between 10 seconds and one minute, preferably between 20 seconds and 50 seconds, after the start of operation of the circuit.

According to one specific embodiment, the circuit also includes a clamping diode (“clamping diode”), the clamping diode being designed to prevent the output voltage from exceeding a threshold value.

This has the advantage that the circuit is protected against overvoltage.

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

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

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 lifetimes in excess of 20 years in demanding industrial applications.

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

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

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

According to one embodiment, the operating device has an insulated or non-insulated DC/DC converter, which is clocked on the primary side and is supplied by the output voltage of the PFC circuit, for supplying a light source.

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

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

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 insulated converter.

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.

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 means by means of a circuit, comprising: supplying a circuit with a supply voltage derived from an AC or DC voltage; providing a regulated output voltage across 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 that is higher than the first temperature range.

character list

• 1 eine schematische Darstellung einer Schaltung zur Niedervolt-Spannungsversorgung einer integrierten Schaltung eines Betriebsgeräts für Leuchtmittel gemäß einer bevorzugten Ausführungsform; und
• 2 eine schematische Darstellung eines Verfahrens zur Niedervolt-Spannungsversorgung einer integrierten Schaltung eines Betriebsgeräts für Leuchtmittel mittels einer Schaltung gemäß einer Ausführungsform.

A brief description of the figures is given below. It shows:

• 1 a schematic representation 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
• 2 a schematic representation of a method for the low-voltage supply of an integrated circuit of an operating device for lamps by means of a circuit according to one embodiment.

5. Detailed description

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.

According to this exemplary embodiment, the circuit 101 shown is fed starting from the output voltage of a PFC circuit. This output voltage typically has a ripple, for example the frequency of a rectified mains voltage.

However, the circuit 101 can also be derived from other DC voltages in an operating device for lighting means, in particular those that are subject to ripple. The circuit 101 is preferably supplied from a voltage on the primary side of an isolated or non-insulated DC/DC converter for supplying a light source.

Circuit 101 includes a storage capacitor 106, circuit 101 being supplied with a supply voltage derived from an AC voltage, and circuit 101 being designed to provide a regulated output voltage at storage capacitor 106. Furthermore, 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 lower than a threshold value than in a second temperature range that is higher than the first temperature range.

In one embodiment, during a start-up phase of the operation of the converter, the setpoint for the supply voltage, which is regulated by a control loop, is selectively set high. This can be done, for example, by a temperature-dependent resistor 110 changing the desired value or the feedback value of the control loop of the low-voltage supply 109 .

In this case, the temperature-dependent resistor 110 is preferably arranged in such a way that it essentially experiences the same temperature as the named storage capacitor 106 .

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

As the temperature increases, the series resistance 105 of the capacitor decreases and the ripple decreases again. It can thus be provided that the increase in the supply voltage is limited to a time range between 10 seconds and one minute, preferably between 20 seconds and 50 seconds. This increase in the supply voltage for a cold start is preferably designed such that it is only active until the temperature at the storage capacitor has increased by 20 degrees relative or above a temperature of, for example -20 degrees (absolute).

So-called clamping diodes 107 can also be provided in the circuit 101, which ensure that the supply voltage does not unintentionally exceed a predetermined range. If it is exceeded, these clamping diodes 107 draw an additional current from the storage capacitor 106, which contributes to the heating of the storage capacitor 106.

The higher ripple can be compensated for by temporarily increasing the low-voltage voltage. This increase in the low-voltage voltage can be implemented, for example, by the temperature-dependent resistor 110. If the device has then heated up, the temperature rises due to the losses in the device and the low-voltage voltage can then drop again.

The low-voltage supply voltage 109 is preferably an LVPS (“low-voltage power supply”) and normally supplies 12V, for example. At low temperatures, a feedback 113 can be manipulated so that the low-voltage supply voltage 109 supplies a slightly increased voltage (e.g. 15V). Many components can exhibit undervoltage lockout. In order to prevent this from being reached at low temperatures, the capacitance of the storage capacitor 106 can be selected to be correspondingly large, or an electrolytic capacitor (Elko) with a low equivalent series resistance 105 (ESR, Hybrid Elko) can be selected.

A few clamping diodes 107, which protect against overvoltage, are preferably provided for 15V operation. Should the clamping become active/conductive, a small part of the LVPS 15V voltage can be short-circuited by the clamping and the critical electrolytic capacitor has a larger load for a short time. This causes the e-cap to heat up and the problem of the too high ESR solving itself.

The operating device 100 for lighting means 116 has the circuit 101 and at least one control unit 112 supplied by this. The control unit 112 can be a microcontroller or an ASIC.

Furthermore, the operating device 100 can have an actively clocked PFC circuit 103, the output voltage of the PFC circuit 103 representing the supply voltage of the circuit 101 for the low-voltage voltage supply of the integrated circuit.

For example, the circuit 100 for the low-voltage power supply of the integrated circuit is arranged on the primary side of the isolated converter 104 .

Alternatively, the circuit for the low-voltage voltage supply of the integrated circuit can also be arranged on the secondary side of the isolated converter 104 .

The operating device 100 can also include an interface 111 , the control unit 112 being designed to clock a switch and/or to communicate with the interface 111 of the operating device 100 .

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

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 .

2 shows a schematic representation of a 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 according to an embodiment.

• - Zuführen 201 einer von einer AC oder DC Spannung abgeleitete Versorgungsspannung einer Schaltung 101;
• - Bereitstellen 202 einer geregelten Ausgangsspannung an einem Speicherkondensator 106, wobei die Schaltung 101 ausgebildet ist, in einem ersten Temperaturbereich, in welchem eine Temperatur der Schaltung und insbesondere des Speicherkondensators 106, kleiner als ein Schwellwert ist, eine höhere Ausgangsspannung bereitzustellen als in einem zweiten Temperaturbereich, der höher als der erste Temperaturbereich ist.

The method 200 for low-voltage power supply 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, the circuit 101 being 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 lower than a threshold value than in a second temperature range , which is higher than the first temperature range.

Claims (15)

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-controlled 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 lower than a threshold value than in a second temperature range which is higher than the first temperature range. Circuit (101) after claim 1 wherein the circuit (101) further comprises a temperature dependent resistor (110) arranged in a feedback path for a signal representative of the output voltage to the low voltage power supply (109). Circuit (101) after claim 2 , wherein the resistor (110) is a PTC thermistor and wherein the resistor (110) is arranged such that it experiences substantially the same temperature as the storage capacitor (106). Circuit (101) after claim 2 or 3 , wherein the low-voltage supply (109) is designed to increase the output voltage as a function of time, e.g. in a period of between 10 seconds and one minute, preferably between 20 seconds and 50 seconds, after the start of operation of the circuit (101). 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 a threshold value of the output voltage being exceeded. 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). A circuit (101) as claimed in any preceding claim, wherein the storage capacitor (106) is an electrolytic capacitor. Operating device (100) for lighting means (106), having a circuit (101) according to one of the preceding claims and at least one control unit (112) supplied by this. Control gear (100) according to claim 8 , wherein the control unit (112) is a microcontroller or an ASIC. Control gear (100) according to one of Claims 8 or 9 , Having 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. Control gear (100) according to claim 10 , having a primary-side clocked isolated or non-isolated DC/DC converter supplied by the output voltage of the PFC circuit (103). Control gear (100) according to claim 10 , wherein the circuit (101) for the low-voltage power supply of an integrated circuit is arranged on the primary side of the isolated converter. Control gear (100) according to claim 10 , in which the circuitry for the low-voltage power supply of an integrated circuit is arranged on the secondary side of the isolated converter. Control gear (100) according to one of Claims 8 until 13 In which the control unit (112) is a control unit for clocking a switch and/or for communicating with an interface (111) of the operating device (100). Method (200) for the low-voltage supply of an integrated circuit of an operating device (100) for lamps (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 across a 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 lower than a threshold value than in a second Temperature range that is higher than the first temperature range.

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