Patent Application
20060291116
The present invention relates to a power supply load selection control circuit and particularly to a load selection control circuit adopted for use on a power supply which has a maximum power utilization limit to enable users to selectively switch and define the required maximum power utilization limit.
Nowadays user's demand for the performance of computer systems increases constantly. Power supply for system CPU and peripheral devices also has to provide a greater power output. Design of the power supply has to take into account of hazard or effect of electricity to human body. Hence there is a limited energy reference for output power (the maximum output power (Max VA) of the power supply mostly is 240 VA under the present specification. Hence for output of 12V, the maximum output current is limited to 20 A). For instance, in SSI or UL standards, there is an Energy Hazard standard for the power supply of electric devices. It limits the maximum output power of the power supply to 240 VA to protect the safety of general computer users.
However, as the operation speed of the computer system increases, the connecting peripheral devices also increase. To meet the requirements of high end users, more electric output ports are needed. Each of the electric output ports has to add a power protection circuit. This creates problems in the fabrication of the power supply, as design of the power protection circuit is difficult. Moreover, different device types require different designs of power protection circuit based on different power. This becomes a heavy burden to power supply manufacturers. In addition, for the high end users, the power required for the high end peripheral devices often is greater than the protection standard. As a result, many high end users prefer the power supply without the protection function. Hence many power supply manufacturers have to design and provide power supply with a greater power but without the protection function to meet market requirements. This also increases the design and fabrication costs. It is not economic effective.
Therefore the primary object of the present invention is to solve the aforesaid disadvantages. The invention aims to provide a power supply load selection control circuit that enables users to selectively determine by themselves different power limit protection functions according to power requirements. Hence power supply manufacturers can produce a single type of uniform product based on a desired power, and users can configure high power peripheral devices without changing different types of power supply.
In order to achieve the foregoing object, the invention is adopted for use on a power supply which has a maximum power utilization limit. The power supply power protection circuit according to the invention provides a limited power value through a power reference circuit. The limited power value is selected and determined through reference elements on the power reference circuit that generate varying power reference values and a switch electrically connected to the reference element circuit. Users can determine the limited power value according to load requirements to optimize the power of the power supply and achieve the protection purpose.
The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
Please refer to ) to determine the limited power value V3 input to the power protection circuit 20.
The power reference circuit 30 for the electric source 31 according to the invention adopts a constant voltage. The power reference circuit 30 is know in the art and has many selections. The invention chooses one of them, such as the electric source 31 with a constant current or a power reference circuit 30 with an equivalent circuit. In one embodiment of the invention, the power protection circuit 20 includes a signal amplifier 21 (presumed to have amplification of 35 times) and a power comparator 22 according to each DC (presumed to be 12V) output to drive the load L1-L3 circuits. The circuits have serial resistors RS1-RS3 (presumed to have an average resistance of 0.002 Ω). When the DC passes through the resistors RS1-RS3, a potential difference is generated. The potential difference is coupled to the + − ends of the signal amplifier 21 and is amplified to get a detected voltage V1. Through sampling resistors RA1-RA3 (presumed to be 2 KΩ) and voltage splitting () of grounded component voltage resistors (
) RV1-RV3 (presumed to be 15 KΩ), a power value V2 is obtained. The power value V2 is connected to a V+ end of the power comparator 22 to become an input signal. The power comparator 22 has a V− end connecting to the power reference circuit 30. The power reference circuit 30 of the invention includes an electric source 31 (presumed to be 2.5 VDC) which passes through power resistors RL1 and RL2 (presumed two maximum power limited modes, with a maximum current limit of 20 A for RL1=1 KΩ, and maximum current limit of 30 A for RL2=510 KΩ), and a component voltage resistor Rs (presumed to be 1 KΩ, the component voltage resistor Rs may be a single power resistor or jointly connected resistors. It is an equivalent circuit. The following discussion is based on two power resistors RL1 and RL2 connecting in parallel). The input signal of the limited power value V3 input to the V− end of the power comparator 22 is determined by the switch 32. The switch 32 may be manually controlled or automatically switched by software definition. If the manual control is adopted, an external switch 71 is provided to do switch control. The switch 71 is located on a face panel 70 of the power supply. There are two indication lights 72 on two sides of the switch 71 to indicate the power conditions after switch is done. For automatic switch by software definition, the switch 32 may be a transistor. And the power protection circuit 20 and the power reference circuit 30 of the invention may be integrated to an IC. This is the design of an equivalent circuit, details are omitted.
Based on the presumed values set forth above, if a user selects the maximum operation current 20 A as the required power protection limit after taking into account of the loads L1-L3, the switch 32 is in an open condition, the input electricity of the electric source 31 merely passes through RL1 without passing through RL2, and the input signal of the limited power value V3 at the receiving end V− of the power comparator 22 may be calculated as follow:
V3=constant voltage(2.5V)×(power resistor RL1=1K Ω/power resistor RL1=1KΩ+component voltage resistor Rs=1KΩ)=1.25V.
The input signal of the use power value V2 at the receiving end V+ of the power comparator 22 may be calculated as follow:
V1=serial resistor RS1(0.0022 Ω)×operation current (20 A)×amplification times(35)=1.4V.
V2=V1×(RA1/RA1+RV1)=1.4×(15 k/15 k+2 k)=1.235V.
Based on above calculations, when the operation current is equal to or smaller than 20 A, the input signal (1.235V) of the use power value V2 at the receiving end V+ of the power comparator 22 is smaller than the input signal (1.25V) of the limited power value V3 at the receiving end V− of the power comparator 22. And the output signal of the power comparator 22 is LOW and does not actuate the protection circuit of the power supply. Hence the power supply functions continuously.
Compare with the example 1, if the output operation current exceeds 20 A due to abnormal condition of the power supply, such as 20.25 A, then V1=1.4175V, and V2 is 1.2507V; and the input signal (1.2507V) of the use power value V2 at the receiving end V+ of the power comparator 22 is greater than the input signal (1.25V) of the limited power value V3 at the receiving end V− of the power comparator 22. The output signal of the power comparator 22 is HIGH and activates the protection circuit of the power supply. The power supply stops operation to avoid generation of hazard energy.
Based on the presumed values set forth above, if a user selects the maximum operation current 30 A as the required power protection limit after taking into account of the loads L1-L3, the switch 32 is in a closed condition. The input electricity of the electric source 31 passes through RL2 and RL1 at the same time, and the input signal of the limited power value V3 at the receiving end V− of the power comparator 22 may be calculated as follow:
V3=constant voltage (2.5V)×(parallel power resistor RL1//RL2=337.75 Ω/power resistor RL1=1KΩ+component voltage resistor Rs=1KΩ)=1.869V.
The input signal of the use power value V2 at the receiving end V+ of the power comparator 22 may be calculated as follow:
V1=serial resistor RS1(0.002 Ω)×operation current (30 A)×amplification times (35)=2.1V.
V2=V1×(RA1/RA1+RV1)=2.1×(15 k/15 k+2 k)=1.853V.
Based on above calculations, when the operation current is equal to or smaller than 30 A, the input signal (1.853V) of the use power value V2 at the receiving end V+ of the power comparator 22 is smaller than the input signal (1.869V) of the limited power value V3 at the receiving end V− of the power comparator 22. And the output signal of the power comparator 22 is LOW and does not actuate the protection circuit of the power supply. Hence the power supply functions continuously.
Compare with the example 1, if the output operation current exceeds 30 A due to abnormal condition of the power supply, such as 30.28 A, and V1=2.1196V, and V2 is 1.87V; then the input signal (1.87V) of the use power value V2 at the receiving end V+ of the power comparator 22 is greater than the input signal (1.869V) of the limited power value V3 at the receiving end V− of the power comparator 22. The output signal of the power comparator 22 is HIGH and activates the protection circuit of the power supply. The power supply stops operation to avoid generation of hazard energy.
According to the examples previously discussed, it is obvious that users can determine the maximum power protection mechanism by themselves according to power requirements of the loads L1-L3 through the switch 32. Hence there is no need to prepare many different specifications of the power supply.
Refer to
While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.
