# US 11,121,622 B2 · Control apparatus of switching power supply for generating drive signal of incremental on-width

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- Number: US 11,121,622 B2
- Document ID: US11121622B2
- Status: Granted
- Kind: B2
- Application number: 16/775,604
- Filed: 2020-01-29
- Published: 2020-09-24
- Granted: 2021-09-14
- Earliest claimed: 2019-03-18
- Assignees: Fuji Electric Co., Ltd.
- Applicants: Fuji Electric Co., Ltd.
- Inventors: Jian Chen; Kiminori Tanaka
- Web page: https://patentgrep.com/patent/US11121622B2

## CPC

- H02M 1/36: Means for starting or stopping converters
- H02M 1/15: using active elements
- H02M 3/01: {Resonant DC/DC converters}
- H02M 3/33571: {Half-bridge at primary side of an isolation transformer}
- H02M 1/0022: {the disturbance parameters being input voltage fluctuations}
- 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)}
- 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 control apparatus of a current resonance type switching power supply that has a switching element and generates an output voltage. The control apparatus includes a drive circuit configured to generate a drive signal to drive the switching element of the switching power supply, and a soft-start control circuit connected to the drive circuit, the soft-start control circuit being configured to send a signal to the drive circuit to cause the drive circuit to increment an on-width of the drive signal by a prescribed step per prescribed switching number, to thereby reduce an overshoot of the output voltage when the switching power supply is started.

## Claims

### Claim 1

A control apparatus of a current resonance type switching power supply that has a switching element and generates an output voltage, the control apparatus comprising:
a drive circuit configured to generate a drive signal to drive the switching element of the switching power supply; and
a soft-start control circuit connected to the drive circuit, the soft-start control circuit being configured to send a signal to the drive circuit to cause the drive circuit to increment an on-width of the drive signal by a prescribed step per prescribed switching number, thereby to gradually increase a switching period of the switching element from a beginning of a soft start period to an end of the soft start period, to gradually decrease a switching frequency of the switching element from the beginning of the soft start period to the end of the soft start period, and to reduce an overshoot of the output voltage when the switching power supply is started, wherein
the soft-start control circuit
implements a first step of holding the on-width of the drive signal for a predetermined time corresponding to the prescribed switching number,
implements a second step of increasing the on-width of the drive signal by the prescribed step after the predetermined time, and
repeats the first step and the second step, alternately.

### Claim 2 (depends on 1)

The control apparatus of the switching power supply according to claim 1, wherein the soft-start control circuit maintains a duty cycle of the drive signal.

### Claim 3 (depends on 1)

The control apparatus of the switching power supply according to claim 1, wherein the soft-start control circuit receives a feedback voltage, and includes
a comparator that detects rising of the feedback voltage,
an on-width set circuit that generates an on-width signal by incrementing the on-width by the prescribed step per prescribed switching number, and
an on-width counter circuit that generates a soft-start turn-off signal indicating a timing at which the generated on-width signal ends.

### Claim 4 (depends on 3)

The control apparatus of the switching power supply according to claim 3, wherein the on-width set circuit includes:
a first counter that counts a number of on-triggers of the drive signal, and outputs a zero flag signal each time the number of on-triggers reaches the prescribed switching number;
a register that holds a value of the on-width;
an adder that adds the prescribed step to the value held in the register;
a first multiplexer that selects the value held in the register when the zero flag signal is not outputted and selects an output of the adder when the zero flag signal is outputted; and
a second multiplexer that selects an initial value of the on-width before the comparator detects the rising of the feedback voltage, selects an output of the first multiplexer after the comparator detects the rising of the feedback voltage, and outputs the selected initial value or the selected output of the first multiplexer to the register.

### Claim 5 (depends on 4)

The control apparatus of the switching power supply according to claim 4, wherein the on-width set circuit includes:
a digital comparator that compares the value held in the register with a maximum on-width signal; and
an AND circuit that disables the zero flag signal only when the value held in the register exceeds the maximum on-width signal.

### Claim 6 (depends on 5)

The control apparatus of the switching power supply according to claim 5, wherein the on-width set circuit includes a self-holding circuit that maintains, when the comparator detects the rising of the feedback voltage, a level of an output of the self-holding circuit.

### Claim 7 (depends on 5)

The control apparatus of the switching power supply according to claim 5, further comprising an input voltage rank determination circuit that determines a rank of input voltages of the switching power supply inputted when the switching power supply is started and outputs a value corresponding to the rank to the on-width set circuit.

### Claim 8 (depends on 7)

The control apparatus of the switching power supply according to claim 7, wherein the value corresponding to the rank includes at least one of the switching number counted by the first counter, the step added by the adder, a minimum on-width signal that is an initial value of the on-width selected by the second multiplexer, or a maximum on-width signal that is a reference input signal of the digital comparator.

### Claim 9 (depends on 3)

The control apparatus of the switching power supply according to claim 3, wherein the on-width counter circuit includes:
a second counter that counts a number of on-triggers of the drive signal, and outputs a zero signal when the number of on-triggers reaches a value of the on-width signal; and
a one-shot circuit that outputs the soft-start turn-off signal having a prescribed on-width based on the zero signal.

### Claim 10

A control apparatus of a current resonance type switching power supply that has a switching element and generates an output voltage, the control apparatus comprising:
a drive circuit configured to generate a drive signal to drive the switching element of the switching power supply;
a soft-start control circuit connected to the drive circuit, the soft-start control circuit being configured to send a signal to the drive circuit to cause the drive circuit to increment an on-width of the drive signal by a prescribed step per prescribed switching number, thereby to gradually increase a switching period of the switching element from a beginning of a soft start period to an end of the soft start period, to gradually decrease a switching frequency of the switching element from the beginning of the soft start period to the end of the soft start period, and to reduce an overshoot of the output voltage when the switching power supply is started; and
an input voltage rank determination circuit that determines a rank based on input voltages of the switching power supply inputted when the switching power supply is started, and outputs a value corresponding to the rank, wherein
the soft-start control circuit
implements a first step of holding the on-width of the drive signal for a predetermined time corresponding to the prescribed switching number,
implements a second step of increasing the on-width of the drive signal by the prescribed step after the predetermined time, and
repeats the first step and the second step, alternately.

### Claim 11 (depends on 10)

The control apparatus of the switching power supply according to claim 10, wherein
the input voltage rank determination circuit outputs, as the value corresponding to the rank, at least one of the prescribed step for incrementing the on-width of the drive signal per prescribed switching number, an initial value of the on-width, a maximum value of the on-width, or the prescribed switching number, to the soft-start control circuit.

### Claim 12 (depends on 1)

The control apparatus of the current resonance type switching power supply according to claim 1, wherein
the control apparatus receives a feedback voltage based on the output voltage,
when the feedback voltage is larger than a first threshold voltage,
the soft-start control circuit implements the first step and the second step, and repeats the first step and the second step, alternately, and
the drive circuit drives the switching element using the on-width of the drive signal and the switching frequency of the switching element according to the first step, the second step, and the alternately repeated first and second steps, and when the feedback voltage is smaller than the first threshold voltage,
the drive circuit stops driving the switching element according to the first step, the second step, and the alternately repeated first and second steps, and
the drive circuit drives the switching element according to the on-width of the drive signal and the switching frequency of the switching element based on the feedback voltage.

### Claim 13 (depends on 10)

The control apparatus of the current resonance type switching power supply according to claim 10, wherein
the control apparatus receives a feedback voltage based on the output voltage,
when the feedback voltage is larger than a first threshold voltage,
the soft-start control circuit implements the first step and the second step, and repeats the first step and the second step, alternately, and
the drive circuit drives the switching element using the on-width of the drive signal and the switching frequency of the switching element according to the first step,
the second step, and the alternately repeated first and second steps, and when the feedback voltage is smaller than the first threshold voltage,
the drive circuit stops driving the switching element according to the first step, the second step, and the alternately repeated first and second steps, and
the drive circuit drives the switching element according to the on-width of the drive signal and the switching frequency of the switching element based on the feedback voltage.