# US 10,770,978 B2 · DC power supply from a constant current source

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- Number: US 10,770,978 B2
- Document ID: US10770978B2
- Status: Granted
- Kind: B2
- Application number: 16/363,643
- Filed: 2019-03-25
- Published: 2019-09-26
- Granted: 2020-09-08
- Earliest claimed: 2018-03-23
- Assignees: Utah State University
- Applicants: Utah State University
- Inventors: Hongjie Wang; Regan A Zane; Tarak Saha
- Web page: https://patentgrep.com/patent/US10770978B2

## CPC

- H02M 3/33573: {Full-bridge at primary side of an isolation transformer}
- H02M 3/01: {Resonant DC/DC converters}
- H02M 3/33571: {Half-bridge at primary side of an isolation transformer}
- H02M 1/0009: {Devices or circuits for detecting current in a converter}
- H02M 1/0058: {by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero (using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826)}
- H02M 7/05: {Capacitor coupled rectifiers}
- Y02B 70/10: Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
- H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P)
- Y02B: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS

## Abstract

A power supply includes an active bridge section with input terminals that receive power from a constant current source where the active bridge section operates at a fixed switching frequency. The power supply includes a resonant section with a resonant inductor and a resonant capacitor. The resonant section is connected to an output of the active bridge section. The power supply includes an output rectifier that receives power from the resonant section and includes output terminals for connection to a load and a controller that regulates output current to the load where the controller regulates output current to the load by controlling switching of the active bridge section. The fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section.

## Claims

### Claim 1

A power supply comprising:
an active bridge section with input terminals that receive power from a constant current source, wherein the active bridge section operates at a fixed switching frequency;
a resonant section comprising a resonant inductor and a resonant capacitor, the resonant section connected to an output of the active bridge section;
an output rectifier that receives power from the resonant section and comprising output terminals for connection to a load; and
a controller that regulates output current to the load, wherein the controller regulates output current to the load by controlling switching of the active bridge section,
wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section, and
wherein the controller regulates output current to the load as a function of current gain from the output current to current from the constant current source by controlling switching of the active bridge section as a single control variable over a range from a minimum load condition to a full load condition.

### Claim 2 (depends on 1)

The power supply of claim 1, wherein the active bridge section comprises a full active bridge, the output rectifier comprises a diode half-bridge voltage doubler and further comprising a transformer between the resonant section and the output rectifier, wherein the controller regulates the current gain as a function of a single control variable of a phase shift angle between switching in a first leg of the active bridge section and a second leg in the active bridge section.

### Claim 3 (depends on 2)

The power supply of claim 2, wherein the controller regulates the current gain according to the equation:
M
I
=
I
out
I
=
1
2
⁢
n
⁢
⁢
sin
⁡
(
α
2
)
where:
MI is the current gain;
Iout is the output current;
I is the current from the constant current source;
n is a turns ratio of the transformer; and
α is the phase shift angle.

### Claim 4 (depends on 1)

The power supply of claim 1, wherein the active bridge section comprises a half-bridge and wherein the controller regulates the current gain as a function of a single control variable of a duty cycle of switches of the active bridge section.

### Claim 5 (depends on 1)

The power supply of claim 1, further comprising a bypass branch connected in parallel with the input terminals, wherein the bypass branch shunts current from the constant current source through the bypass branch when the bypass branch is active.

### Claim 6 (depends on 5)

The power supply of claim 5, wherein the bypass branch comprises a sensing resistor in series with a shunt switch comprising a transistor, wherein the controller operates the shunt switch in an active region of the transistor to shunt current from the constant current source in a range between zero current and a full current of the constant current source, wherein the shunt switch is operable to shunt a portion of the current of the constant current source.

### Claim 7 (depends on 1)

The power supply of claim 1, further comprising a resonant capacitor voltage clamping circuit that clamps voltage across the resonant capacitor to a voltage less than a maximum voltage rating of the resonant capacitor during a transient condition.

### Claim 8 (depends on 7)

The power supply of claim 7, wherein the resonant capacitor voltage clamping circuit comprises a diode full-bridge rectifier with an input of the diode full-bridge rectifier connected across the resonant capacitor and an output of the diode full-bridge rectifier connected in parallel with a clamping capacitor and connected in parallel with a bleeder resistor, wherein during steady-state operation, voltage across the clamping capacitor is higher than a voltage rating of the resonant capacitor.

### Claim 9 (depends on 1)

The power supply of claim 1, further comprising a current limiting circuit connected in series between an output terminal of the output rectifier and the load, wherein the current limiting circuit increases a resistance across the current limiting circuit in response to output current to the load increasing above an output current limit.

### Claim 10 (depends on 9)

The power supply of claim 9, wherein the current limiting circuit comprises a current limiting switch in series with a sensing resistor, the current limiting switch comprising a transistor, wherein voltage across the sensing resistor is connected to a control terminal of the transistor and wherein a voltage level across the sensing resistor activates an active region of the transistor and wherein a current increase in the sensing resistor increases a resistance across the transistor.

### Claim 11

A power supply comprising:
an active bridge section with input terminals that receive power from a constant current source;
a resonant section comprising a resonant inductor and a resonant capacitor, the resonant section connected to an output of the active bridge section;
an output rectifier that receives power from the resonant section and comprising output terminals for connection to a load;
a controller that regulates output current to the load;
a bypass branch connected in parallel with the input terminals, wherein the bypass branch shunts current from the constant current source through the bypass branch when the bypass branch is active;
a resonant capacitor voltage clamping circuit that clamps voltage across the resonant capacitor to a voltage less than a maximum voltage rating of the resonant capacitor during a transient condition; and
a current limiting circuit connected in series between an output terminal of the output rectifier and the load, wherein the current limiting circuit increases a resistance across the current limiting circuit in response to output current to the load increasing above an output current limit,
wherein the active bridge section operates at a fixed switching frequency, wherein the controller regulates output current to the load by controlling switching of the active bridge section, and wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section, and
wherein the controller regulates output current to the load as a function of current gain from the output current to current from the constant current source by controlling switching of the active bridge section as a single control variable over a range from a minimum load condition to a full load condition.

### Claim 12 (depends on 11)

The power supply of claim 11, wherein the active bridge section comprises a full active bridge, the output rectifier comprises a diode half-bridge voltage doubler and further comprising a transformer between the resonant section and the output rectifier, wherein the controller regulates the current gain as a function of a single control variable of a phase shift angle between switching in a first leg of the active bridge section and a second leg in the active bridge section.

### Claim 13 (depends on 11)

The power supply of claim 11, wherein the bypass branch comprises a sensing resistor in series with a shunt switch comprising a transistor, wherein the controller operates the shunt switch in an active region of the transistor to shunt current from the constant current source in a range between zero current and a full current of the constant current source, wherein the shunt switch is operable to shunt a portion of the current of the constant current source.

### Claim 14 (depends on 11)

The power supply of claim 11, wherein the resonant capacitor voltage clamping circuit comprises a diode full-bridge rectifier with an input of the diode full-bridge rectifier connected across the resonant capacitor and an output of the diode full-bridge rectifier connected in parallel with a clamping capacitor and connected in parallel with a bleeder resistor, wherein during steady-state operation voltage across the clamping capacitor is higher than a voltage rating of the resonant capacitor.

### Claim 15 (depends on 11)

The power supply of claim 11, wherein the current limiting circuit comprises a current limiting switch in series with a sensing resistor, the current limiting switch comprising a transistor, wherein voltage across the sensing resistor is connected to a control terminal of the transistor and wherein a voltage level across the sensing resistor activates an active region of the transistor and wherein a current increase in the sensing resistor increases a resistance across the transistor.

### Claim 16

A controller comprising:
an output current regulation feedback loop that regulates output current of a power supply to a load, wherein the controller regulates output current to the load by controlling switching of an active bridge section of the power supply, the power supply comprising:
a resonant section comprising a resonant inductor and a resonant capacitor, the resonant section connected to an output of the active bridge section, the active bridge section comprising input terminals that receive power from to a constant current source, wherein the active bridge section operates at a fixed switching frequency; and
an output rectifier that receives power from the resonant section and comprising output terminals for connection to the load,
wherein the fixed switching frequency of the active bridge section matches a resonant frequency of the resonant section, and
wherein the controller regulates output current to the load as a function of current gain from the output current to current from the constant current source by controlling switching of the active bridge section as a single control variable over a range from a minimum load condition to a full load condition.

### Claim 17 (depends on 16)

The power supply of claim 16, further comprising:
a bypass branch connected in parallel with the input terminals, wherein the bypass branch shunts current from the constant current source through the bypass branch when the bypass branch is active;
a resonant capacitor voltage clamping circuit that clamps voltage across the resonant capacitor to a voltage less than a maximum voltage rating of the resonant capacitor during a transient condition; and
a current limiting circuit connected in series between an output terminal of the output rectifier and the load, wherein the current limiting circuit increases a resistance across the current limiting circuit in response to output current to the load increasing above an output current limit.