Power transfer over an isolated capacitive barrier with controlled current
In one example, an apparatus comprises: a primary side bridge coupled between a power input and a first ground terminal, the primary side bridge having first switching terminals coupled to first capacitor terminals; and a secondary side bridge coupled between a power output and a second ground terminal, the secondary side bridge having second switching terminals coupled to second capacitor terminals.
1 . An apparatus comprising:
a primary side bridge coupled between a power input and a first ground terminal, the primary side bridge having first switching terminals coupled to first isolation terminals;
a secondary side bridge coupled between a power output and a second ground terminal, the secondary side bridge having second switching terminals coupled to second isolation terminals; and
a configurable current source coupled to at least one of the primary side bridge or the secondary side bridge.
2 . The apparatus of claim 1 , further comprising capacitors coupled between the first isolation terminals and the second isolation terminals.
3 . The apparatus of claim 2 , wherein the first switching terminals include a first switching terminal and a second switching terminal each coupled to a respective one of the first isolation terminals, and the second switching terminals include a third switching terminal and a fourth switching terminal each coupled to a respective one of the second isolation terminals.
4 . The apparatus of claim 3 , wherein the capacitors include a first capacitor coupled between the first switching terminal and the third switching terminal and a second capacitor coupled between the second switching terminal and the fourth switching terminal.
5 . The apparatus of claim 3 , wherein:
the primary side bridge includes:
a first transistor coupled between the power input and the first switching terminal, and a second transistor coupled between the first switching terminal and the first ground terminal; and
a third transistor coupled between the power input and the second switching terminal, and a fourth transistor coupled between the second switching terminal and the first ground terminal; and
the secondary side bridge includes:
a fifth transistor coupled between the power output and the third switching terminal, and a sixth transistor coupled between the third switching terminal and the second ground terminal; and
a seventh transistor coupled between the power output and the fourth switching terminal, and an eighth transistor coupled between the fourth switching terminal and the second ground terminal.
6 . The apparatus of claim 5 , further comprising a controller coupled to the first through eighth transistors, the controller configurable to, responsive to a multi-cycle clock signal:
in a first half of a cycle period of the clock signal: enable the first, fourth, fifth, and eighth transistors, and disable the second, third, sixth, and seventh transistors; and
in a second half of the cycle period: disable the first, fourth, fifth, and eighth transistors, and enable the second, third, sixth, and seventh transistors.
7 . The apparatus of claim 5 , further comprising a controller coupled to the first through eighth transistors, the controller configurable to, responsive to a multi-cycle clock signal:
in a first half of a cycle period of the clock signal: enable the first, fourth, fifth, and eighth transistors, and disable the second, third, sixth, and seventh transistors; and
in a second half of the cycle period: disable the first, fourth, fifth, and seventh transistors, and enable the second, third, sixth, and eighth transistors.
8 . The apparatus of claim 5 , wherein the current source is coupled between a terminal of the secondary side bridge and the power output, the current source configurable to set a first current from the first switching terminal to the third switching terminal when the first and sixth transistors are enabled, and to set a second current from the fourth switching terminal to the second switching terminal when the fourth and seventh transistors are enabled.
9 . The apparatus of claim 8 , further comprising a controller coupled to the current source and configurable to set a current provided by the current source responsive to a difference between a voltage between the power output and the second ground terminal and a reference voltage.
10 . The apparatus of claim 5 , wherein the current source is coupled between the power input and a terminal of the primary side bridge, the current source configurable to set a first current from the first switching terminal to the third switching terminal when the first and sixth transistors are enabled, and to set a second current from the fourth switching terminal to the second switching terminal when the fourth and seventh transistors are enabled.
11 . The apparatus of claim 10 , wherein the current source is a first current source, and the apparatus further comprises: a second current source coupled between the primary side bridge and the first ground terminal, the first and second current sources are configurable to conduct a same amount of current; and
a controller coupled to the first and second current sources and configurable to set the current responsive to a voltage difference between the first switching terminals.
12 . The apparatus of claim 11 , wherein each of the first and second current sources is configurable to conduct a fraction of a current provided by the secondary side bridge.
13 . The apparatus of claim 2 , wherein each of the capacitors is a Y-rated capacitor.
14 . The apparatus of claim 2 , wherein the primary side and secondary side bridges are in a packaged integrated circuit, and the capacitors are external to the packaged integrated circuit.
15 . The apparatus of claim 1 , further comprising an analog front end having a sensor interface, a power terminal, and a reference terminal, the power terminal coupled to the power output, and the reference terminal coupled to the second ground terminal.
16 . The apparatus of claim 15 , wherein the analog front end includes an analog to digital converter (ADC) having an analog input coupled to the sensor interface.
17 . The apparatus of claim 15 , wherein the analog front end includes a sensor having a sensor output coupled to the sensor interface.
18 . The apparatus of claim 15 , wherein the analog front end includes a sensor having a sensor output coupled to the sensor interface.
19 . The apparatus of claim 1 , further comprising a fieldbus interface circuitry coupled to the power input, the fieldbus interface circuitry including the primary side bridge.
20 . An apparatus comprising:
a primary side bridge coupled between a power input and a first ground terminal, the primary side bridge having first switching terminals coupled to first capacitor terminals, the primary side bridge configurable to transmit a first current and receive a second current via the first capacitor terminals; and
a secondary side bridge coupled between a power output and a second ground terminal, the secondary side bridge having second switching terminals coupled to second capacitor terminals, the secondary side bridge configurable to receive the first current and transmit the second current via the second capacitor terminals.
21 . The apparatus of claim 20 , further comprising capacitors coupled between the first capacitor terminals and the second capacitor terminals.
22 . The apparatus of claim 21 , wherein the capacitors include Y-rated capacitors.
23 . The apparatus of claim 20 , further comprising a configurable current source coupled to at least one of the primary side bridge or the secondary side bridge, wherein a current provided by the current source is configurable responsive to a first voltage between the first switching terminals or a second voltage between the power output and the second ground terminal.
24 . The apparatus of claim 23 , wherein the configurable current source includes a transistor.
25 . An apparatus comprising:
a primary side switch circuit coupled between a power input and a first ground terminal, the primary side switch circuit having first terminals coupled to first and second capacitor terminals, the primary side switch circuit configurable to transmit a first current via the first capacitor terminal and receive a second current via the second capacitor terminal; and
a secondary side switch circuit coupled between a power output and a second ground terminal, the secondary side switch circuit having second terminals coupled to third and fourth capacitor terminals, the secondary side switch circuit configurable to receive the first current via the third capacitor terminal and transmit the second current via the fourth capacitor terminals.
26 . The apparatus of claim 25 , wherein the primary side switch circuit is configurable to transmit the first current as a first current pulse that decays to zero in a first half of a switching cycle, and the secondary side switch circuit is configurable to transmit the second current as a second current pulse that decays to zero in a second half of the switching cycle.
27 . The apparatus of claim 26 , wherein a voltage between the first ground terminal and the second ground terminal switches between a positive value and a negative value within the switching cycle.
28 . The apparatus of claim 26 , further comprising a controller configurable to set a duration of the switching cycle responsive to a first voltage between the power input and the first ground terminal and a second voltage between the power output and the second ground terminal.
29 . The apparatus of claim 25 , further comprising a current source coupled to the secondary side switch circuit, the current source configurable to set the second current responsive to a voltage between the power output and the second ground terminal.
30 . The apparatus of claim 25 , further comprising a current source coupled to the primary side switch circuit, the current source configurable to set the first current responsive to a voltage between the first and second capacitor terminals.
31 . The apparatus of claim 25 , wherein the first current is constant within a first half of a switching cycle, and the second current is constant within a second half of the switching cycle.
32 . The apparatus of claim 31 , wherein a voltage between the first ground terminal and the second ground terminal includes a first ramp in the first half of the switching cycle and a second ramp in the second half of the switching cycle, the first and second ramps having opposite directions.