Detection circuit
A detection circuit for generating a control signal for controlling output voltage of an AC adapter. The detection circuit for an electronic device receives power information from an external power supply via a cable to generate the control signal that controls DC input voltage output from the external power supply. In the detection circuit, a correction voltage generation circuit generates a correction voltage in correspondence with the parasitic resistance of the cable. A power information correction circuit corrects the power information provided from the external power supply via the cable with the correction voltage to generate corrected power information. A detection signal generation circuit calculates the total power amount of the electronic device and generates a power detection signal corresponding to the total power amount. The control signal generation circuit generates the control signal based on the corrected power information and the power detection signal.
1. A detection circuit for generating a control signal for controlling direct current input voltage generated by an external power supply based on power information provided from the external power supply via a cable, the detection circuit comprising:
a correction voltage generation circuit that generates correction voltage in accordance with a parasitic resistance of the cable;
a power information correction circuit coupled to the correction voltage generation circuit to receive the power information via the cable in which the power information correction circuit corrects the power information with the correction voltage and generates corrected power information;
a detection signal generation circuit that calculates a total power amount from the input voltage and input current, which is supplied from the external power supply, to generate a power detection signal corresponding to the total power amount; and
a control signal generation circuit coupled to the power information correction circuit and the detection signal generation circuit to generate the control signal from the corrected power information and the power detection signal.
2. The detection circuit according to claim 1 , wherein the correction voltage generation circuit includes:
a correction current generation circuit that generates a correction current in accordance with the input current; and
a resistor circuit coupled to the correction current generation circuit and having a resistance value corresponding to the parasitic resistance of the cable, wherein the correction voltage is generated at a node between the correction current generation circuit and the resistor circuit based on the resistance value and the correction current.
3. The detection circuit according to claim 2 , wherein the resistor circuit includes a plurality of resistors, and one or more of the plurality of resistors is used in accordance with the parasitic resistance of the cable.
4. The detection circuit according to claim 2 , further comprising:
a current amplifier that generates a current detection signal corresponding to the input current;
wherein the correction current generation circuit is coupled to the current amplifier and generates the correction current based on the current detection signal.
5. The detection circuit according to claim 1 , wherein the power information generation circuit generates the corrected power information by adding the correction voltage to the power information.
6. The detection circuit according to claim 1 , further comprising:
a current amplifier for generating a current detection signal corresponding to the input current;
wherein the correction voltage generation circuit is coupled to the current amplifier and generates the correction voltage based on the current detection signal; and
the power information generation circuit generates the corrected power information by adding the correction voltage to the power information.
7. The detection circuit according to claim 1 , further comprising:
a current amplifier for generating a current detection signal corresponding to the input current;
the control signal generation circuit including:
a first error amplifier coupled to the current amplifier to compare the current detection signal with a current reference signal and generate a first error voltage; and
a second error amplifier coupled to the power information correction circuit and the detection signal generation circuit to compare the corrected power information with the power detection signal and generate a second error voltage, wherein either one of the first error voltage and the second error voltage is output as the control signal; and
wherein the correction voltage generation circuit is coupled to the current amplifier to generate the correction voltage based on the current detection signal.
8. A power supply system comprising:
an external power supply that generates direct current input voltage; and
an electronic device that operates on the input voltage supplied from the external power supply via a cable, wherein:
the external power supply includes a voltage control circuit that generates the input voltage and provides power information corresponding to the input voltage to the electronic device via the cable; and
the electronic device includes a detection circuit for generating a control signal that controls the input voltage based on the power information, the detection circuit including:
a correction voltage generation circuit that generates correction voltage in accordance with a parasitic resistance of the cable;
a power information correction circuit coupled to the correction voltage generation circuit to receive the power information via the cable in which the power information correction circuit corrects the power information with the correction voltage and generates corrected power information;
a detection signal generation circuit that calculates a total power amount of the electronic device from the input voltage and input current, which is supplied from the external power supply to the electronic device and generates a power detection signal corresponding to the total power amount; and
a control signal generation circuit coupled to the power information correction circuit and the detection signal generation circuit to generate the control signal based on the corrected power information and the power detection signal.
9. The power supply system according to claim 8 , wherein the correction voltage generation circuit includes:
a correction current generation circuit that generates a correction current in accordance with the input current; and
a resistor circuit coupled to the correction current generation circuit and having a resistance value corresponding to the parasitic resistance of the cable, wherein the correction voltage is generated at a node between the correction current generation circuit and the resistor circuit based on the resistance value and the correction current.
10. The power supply system according to claim 9 , wherein the resistor circuit includes a plurality of resistors, and one or more of the plurality of resistors is selected in accordance with the parasitic resistance of the cable.
11. The power supply system according to claim 9 , wherein:
the detection circuit further includes a current amplifier that generates a current detection signal corresponding to the input current; and
the correction current generation circuit is coupled to the current amplifier and generates the correction current based on the current detection signal.
12. The power supply system according to claim 8 , wherein the power information generation circuit generates the corrected power information by adding the correction voltage to the power information.
13. The power supply system according to claim 8 , wherein:
the detection circuit further includes a current amplifier for generating a current detection signal corresponding to the input current;
the correction voltage generation circuit is coupled to the current amplifier and generates the correction voltage based on the current detection signal; and
the power information generation circuit generates the corrected power information by adding the correction voltage to the power information.
14. The power supply system according to claim 8 , wherein:
the detection circuit further includes a current amplifier for generating a current detection signal corresponding to the input current;
the control signal generation circuit includes:
a first error amplifier coupled to the current amplifier to compare the current detection signal with a current reference signal and generate a first error voltage; and
a second error amplifier coupled to the power information correction circuit and the detection signal generation circuit to compare the corrected power information with the power detection signal and generate a second error voltage, wherein either one of the first error voltage and the second error voltage is output as the control signal; and
the correction voltage generation circuit is coupled to the current amplifier to generate the correction voltage based on the current detection signal.
15. A method for controlling direct current input voltage generated by an external power supply based on power information provided from the external power supply comprising:
receiving the power information via a cable;
generating correction voltage in accordance with a parasitic resistance of the cable;
correcting the power information with the correction voltage to generate corrected power information;
calculating a total power amount from the input voltage and input current, which is supplied from the external power supply, to generate a power detection signal corresponding to the total power amount; and
generating a control signal from the corrected power information and the power detection signal.
16. The method according to claim 15 , wherein the generation of the control signal is performed in an electronic device coupled to the external power supply via the cable.