Fan controller

Abstract

Fan controller (1) for a modular power supply having a fan (13). An output (8) is provided for transmitting control signals to the fan (13) for controlling fan speed. A plurality of sensor modules (20) are associated with a respective module (11, 6, 7) of the modular power supply. Each sensor module (20) includes a temperature detecting circuit comprising a sensor for sensing temperature variations in the respective module (11, 6, 7), a fan control circuit (30) galvanically isolated from the temperature detecting circuit for outputting a control signal to the output (8) for controlling the fan (13), and an optocoupler (10,9) for transferring an output signal from the temperature detecting circuit (20) to the fan control circuit (30) for generating the control signal.

Claims

1. A fan controller for a modular power supply having a mains input side, a low voltage output side comprising a plurality of galvanically isolated output modules, and a fan, the fan controller comprising: an output for transmitting control signals to the fan for controlling fan speed; and a plurality of sensor modules each sensor module associated with a respective one of the plurality of output modules of the modular power supply, wherein each sensor module comprises: a temperature detecting circuit comprising a sensor for sensing temperature variations in the respective module; a fan control circuit galvanically isolated from the temperature detecting circuit for outputting a control signal to the output for controlling the fan; and an optocoupler for transferring an output signal from the temperature detecting circuit to the fan control circuit for generating the control signal.

2. The fan controller according to claim 1, wherein the temperature detecting circuit comprises an operational amplifier for generating the output signal.

3. The fan controller according to claim 2, wherein the operational amplifier is configured as a bridge.

4. The fan controller according to claim 2, wherein the operational amplifier comprises negative feedback.

5. The fan controller according to claim 1, wherein the temperature detecting circuit has a set-point corresponding to an activation temperature and generates the output signal when the temperature sensed by the sensor exceeds the activation temperature.

6. The fan controller according to claim 1, wherein the sensor is a thermistor.

7. The fan controller according to claim 1, wherein the optocoupler comprises a light-emitting component connected to the temperature detecting circuit and a light detecting component connected to the fan control circuit.

8. The fan controller according to claim 7, wherein the light-emitting component is a light-emitting diode.

9. The fan controller according to claim 7, wherein the light detecting component is a photodiode or a phototransistor.

10. The fan controller according to claim 1, wherein the fan control circuits of the plurality of sensor modules are connected to the output in a wired OR arrangement.

11. The fan controller according to claim 1, wherein, in use, the output transmits the sum of the control signals from the plurality of sensor modules to the fan for controlling fan speed.

12. The fan controller according to claim 1, wherein the output comprises a digital filter for filtering the control signals transmitted to the fan.

13. The fan controller according to claim 12, wherein the digital filter has a pole at 0.01 Hz.

14. The fan controller according to claim 1, wherein the output comprises a low pass filter for filtering the control signals transmitted to the fan.

15. A power supply comprising: a mains input side; a low voltage output side comprising a plurality of output modules; a fan for cooling the plurality of modules, the fan having an input for receiving a control signal for controlling the fan's speed; and a plurality of sensor modules, each sensor module associated with a respective output module of the plurality of output modules of the modular power supply, wherein each sensor module comprises: a temperature detecting circuit comprising a sensor for sensing temperature variations in the respective module; a fan control circuit galvanically isolated from the temperature detecting circuit for outputting a control signal to the fan's input for controlling the fan; and an optocoupler for transferring an output signal from the temperature detecting circuit to the fan control circuit for generating the control signal.

Description

(1) Illustrative embodiments of the present invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1 shows a circuit diagram for an embodiment of the present invention; and

(3) FIG. 2 shows a schematic diagram of the embodiment shown in FIG. 1.

(4) FIG. 1 shows a circuit diagram for a fan controller 1 according to an embodiment of the present invention.

(5) The fan controller 1 comprises a temperature sensor 2 which is located close to a hotspot on a first module of a modular power supply for sensing its operating temperature. In this embodiment, the temperature sensor 2 is an NTC negative temperature coefficient (NTC) thermistor, although other temperature sensors, such as a positive temperature coefficient (PTC) thermistors may be used.

(6) The temperature sensor 2 is connected to the non-inverting input of the operational amplifier (op-amp) 3. As the temperature sensed by NTC temperature sensor 2 increases, its resistance decreases, thereby increasing the voltage applied to the non-inverting input of op-amp 3.

(7) The op-amp 3 is provided with a negative feedback loop connecting a resistor and capacitor in parallel between the op-amp's output and its inverting input. The input of the op-amp is configured as a bridge, which thereby avoids the need for a stable reference voltage to supply the temperature sensor 2. The op-amp 3 is configured to have a predetermined set-point which corresponds to an activation temperature sensed by the temperature sensor 2. That is, when the temperature sensor 2 is exposed to a temperature above the activation temperature, the voltage applied to the non-inverting input increases above a threshold, triggering the op-amp 3 to generate an output signal. The op-amp 3 and temperature sensor 2 thereby forms a sensing circuit 20 which activates once the set-point is reached.

(8) The output of op-amp 3 is connected to an optocoupler 4 for transmitting signals across an isolation barrier from the sensing circuit 20 to a control circuit 30 connected to the fan (not shown). In particular, the op-amp's output connects to a light-emitting diode (LED) 10 of the optocoupler 4 which emits a light signal when the output signal is generated by op-amp 3. On the control circuit 30 side of the optocoupler, a phototransistor 9 receives the light signals emitted by the LED 10, and in turn generates a control signal in the output 8 in response thereto. Output 8 is connected to the control terminal of the fan and the application of the generated control signal causes the fan speed to increase.

(9) FIG. 1 further shows the phototransistors of a second 6 and third optocoupler 7 which are associated with second and third modules of the modular power supply, respectively. As such, each optocoupler has its own temperature sensor and op-amp which form part of sensing module associated with each respective power supply module. The phototransistors of the second 6 and third optocoupler are connected, along with the phototransistor 9 of the first optocoupler 4, to the output 8 in a wired-OR arrangement. As such, in use, if any modules' temperature sensors 2 exceed their activation temperature, a control signal will be generated by the respective optocoupler 4, 6, 7 in the output 8, thereby controlling the fan to increase fan speed. As such, the fan 13 may be controlled by any one of the sensor modules through only one input 8. It will be understood that different modules may be configured to have different set points in order to optimise the temperature at which they activate the fan depending on, for example, the temperature sensitivity of the components within that module.

(10) FIG. 2 shows a schematic diagram of the embodiment shown in FIG. 1. As shown, the controller 1 is provided with three sensing modules 11, 6, 7 which are associated with different modules of the modular power supply. The temperature detecting circuits 20 of each module 11, 6, 7 are galvanically isolated from one another. At the same time, the LEDs 10 and the phototransistors 9 of the modules 11, 6, 7 form an isolation barrier 12 between each module's temperature detecting circuit 20 and control circuit 30. The control circuits 30 are connected to a common output 8 which allows any one or more of the modules 11, 6, 7 to control the speed of fan 13. In use, the fan 13 may be configured to operate at a low speed setting by default. If the temperature in any of the sensing modules 11, 6, 7 then reaches its activation temperature, a control signal will be generated in the output 8 to activate a higher speed setting on the fan 13.

(11) In embodiments, the fan speed may increase with the magnitude of the current applied through output 8. For example, the fan 13 may be controlled so that its speed is proportional to the sum of the received one or more control signals; as further modules reach their activation temperature, the fan speed may therefore increase further.

(12) Accordingly, with embodiments of the present invention, the controller does not attempt to determine how hot the individual modules are, but instead identifies that one or more of the modules have reached their respective activation temperatures determined by the set-point of their control loops. This thereby provides for a small, cheap and simple fan controller, in which only one inexpensive, low-speed optocoupler is required per module. The wired-OR arrangement also means that a number of modules may be connected, limited only by the leakage current of whichever type of optocoupler is used.

(13) In some embodiments, a slow digital filter 14 may additionally be provided at the output 8 for stabilising the feedback control loop. For example, a digital filter 14 may be provided in the microprocessor used for fan control to create a pole at 0.01 Hz. A low pass filter 15 may also be provided to remove noise in the system. This may help to mitigate any control instability arising from the thermal mass and time-constant of each module.

(14) It will be understood that the embodiment illustrated above shows applications of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

(15) For example, although the above embodiment describes the invention in the context of a modular PSU with three modules, it will be understood that the invention may be applied to PSU's with different numbers of modules. For example, two or more sensing modules may be provided. Furthermore, more than one sensing module may be associated with a single PSU module to provide temperature sensing at two locations within the same module.

(16) Furthermore, embodiments providing some additional analogue control over the fan speed may also be implemented. For example, the optocoupler may be provided with an analogue response such that, when the output of the op-amp increases with increasing temperature, the intensity of the signal transmitted by the optocoupler may also increase. This may then cause the control signal current to increase, thereby increasing the fan speed. In embodiments, the op-amp may be configured such that the varying output signal is only generated above the set-point, once the activation temperature has been exceeded.